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Why is polio still around? · Health Matters

• 0:00
  Speaker 1: Health Matters with Daniel Martin.
• 0:03
  Speaker 1: It's Health Matters. Welcome aboard, everybody. Thank you so much
• 0:05
  Speaker 1: for joining me, Daniel Martin. Many of you would have
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  Speaker 1: heard about or read about on CNA.Asia how Singapore's confirmed
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  Speaker 1: one imported case of vaccine associated polio. It was an
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  Speaker 1: infant who was flown in from I came in from
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  Speaker 1: Indonesia and taken directly to NUH upon arrival in Singapore
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  Speaker 1: and then isolated upon admission.
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  Speaker 1: We want to know more about why are we still
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  Speaker 1: hearing about polio and what is vaccine associated polio as well.
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  Speaker 1: I'm pleased to welcome Doctor Nicholas Chuu, infectious disease specialist,
• 0:33
  Speaker 1: Fair Park Hospital, joining us on today's edition of Health Matters.
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  Speaker 1: It's been a wild off you. Hello, welcome back to
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  Speaker 1: the show.
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  Speaker 2: Hi, um, yeah, so polio is a highly contagious virus
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  Speaker 2: that causes an infection, and really the, the concern is
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  Speaker 2: that the virus will infect the spinal cord, and this
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  Speaker 2: might lead to a severe disabling and also potentially life-threatening condition.
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  Speaker 1: I was talking to some of my colleagues before the
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  Speaker 1: show began who are all very interested in this topic
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  Speaker 1: and they say, yeah, yeah, yeah, because they're of a
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  Speaker 1: certain age and they're like, I remember in the 60s
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  Speaker 1: and 70s, people were really affected by this and it
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  Speaker 1: was highly contagious. So it was highly contagious and it
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  Speaker 1: was preval not prevalent, but it was common in Singapore.
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  Speaker 2: Um, well, the polio vaccine's been rolled out in Singapore
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  Speaker 2: since 1962, and, and obviously, it's, it's, it's taken off.
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  Speaker 2: It's not mandated by law, but I think the uptake is, is,
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  Speaker 2: is very robust in Singapore. And as a result, you know, we,
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  Speaker 2: we haven't seen any local transmission of, of cases since 1972.
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  Speaker 1: So, in
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  Speaker 2: fact, the last reported case was in, uh, 2006, and
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  Speaker 2: that was also an
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  Speaker 2: And uh imported case, same as the current one. OK,
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  Speaker 1: so the full name for it is poliomyelitis. uh,
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  Speaker 2: it's polio virus that causes a condition called poliomyelitis. So myelitis, uh, uh, uh,
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  Speaker 2: refers to inflammation of the spinal cord and therefore you
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  Speaker 2: get all the paralysis in your limbs and it could also,
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  Speaker 2: also affect your, your, uh, diaphragm, i.e. your breathing muscles,
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  Speaker 2: and that could impair someone's ability to breathe.
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  Speaker 1: And how is it transmitted?
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  Speaker 2: Um, well, polio is normally acquired through, through the oral route.
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  Speaker 2: So say if you have a patient who's contagious, they
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  Speaker 2: will be shedding the virus through their, their oral secretions.
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  Speaker 2: Then the virus kind of passes through your gut and
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  Speaker 2: it starts to replicate in the bowel. And because of that, your,
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  Speaker 2: your index patient will then start to secrete the virus
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  Speaker 2: in the feces.
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  Speaker 1: So fecal oral transmission,
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  Speaker 2: correct. So most likely this patient would, uh, well, I
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  Speaker 2: suppose this particular infant would be different, but, uh, in
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  Speaker 2: general for most patients, they would have acquired it through
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  Speaker 2: contamination of whatever.
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  Speaker 2: So
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  Speaker 1: in the past, it could have been, yeah, through food
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  Speaker 1: prepared by people who've not washed their hands, for example,
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  Speaker 1: or I guess,
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  Speaker 2: you know, sharing of saliva or respiratory secretions, for
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  Speaker 2: example.
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  Speaker 1: It can be transmitted in the saliva and respiratory secretions
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  Speaker 1: as well. It's not necessarily just oral fecal
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  Speaker 1: transmission,
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  Speaker 2: not necessarily. So if someone in the acute phase is infectious, uh,
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  Speaker 2: they will start producing the, the virus in, in their
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  Speaker 2: mouth as well.
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  Speaker 1: I go for something to be transmitted so easily and
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  Speaker 1: to have such deleterious effects on the individual as well. No,
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  Speaker 1: no wonder the world celebrated when we so-called eradicated polio.
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  Speaker 1: Doctor Chu, why are we still talking about polio if
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  Speaker 1: we supposedly eradicated it?
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  Speaker 2: Well, um, as of 2020, um, polio has been largely
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  Speaker 2: eradicated in most parts of the world, but what we
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  Speaker 2: don't know is that there are still 22 countries in
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  Speaker 2: the world where polio is endemic, i.e. Afghanistan and Pakistan, OK.
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  Speaker 2: Um, but the current imported case probably has, uh, uh,
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  Speaker 2: been the polio infection has been acquired as a result of,
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  Speaker 2: of vaccination potentially.
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  Speaker 1: Let's talk about that. The articles are saying, um, vaccine
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  Speaker 1: associated polio. What is vaccine associated polio by definition?
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  Speaker 2: Well, the, the WHO term for this is actually VDPV,
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  Speaker 2: which is vaccine-derived poliovirus.
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  Speaker 2: So to understand that, um, um, you need to appreciate
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  Speaker 2: that there are currently two types of polio vaccines. The
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  Speaker 2: first one is the oral uh vaccine, which is OPV
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  Speaker 2: or the inactivated vaccine, which is IPV, OK? Um, traditionally,
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  Speaker 2: we would have used the oral vaccine.
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  Speaker 2: Uh, for, and the oral vaccine remains the mainstay of
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  Speaker 2: vaccination for large parts of the world. And the reason
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  Speaker 2: for that is because it's, um, you don't need to
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  Speaker 2: inject it. You just put it into an infant's mouth.
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  Speaker 2: So because of that, you get easier access, um, um,
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  Speaker 2: but the problem with the oral vaccine is that it's
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  Speaker 2: actually a live virus. It's a live attenuated virus, which
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  Speaker 2: means that the virus has been weakened.
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  Speaker 2: So in general, in, in uh uh a healthy uh infant,
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  Speaker 2: healthy host, um, the immune system will, will keep that
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  Speaker 2: under check.
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  Speaker 1: So live attenuated the virus, the concept is I introduce
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  Speaker 1: a weakened form of the virus to your body and
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  Speaker 1: your body develops immunity against
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  Speaker 1: it.
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  Speaker 2: It's almost as if you were, you were infecting somebody with,
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  Speaker 2: with polio, but because it's a weakened form, you're not
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  Speaker 2: likely to develop severe complications from it, OK? But the
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  Speaker 2: caveat to that is that if you use the oral
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  Speaker 2: vaccine in, in the live viral form in an immunocompromised host,
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  Speaker 2: what might happen then is this live virus might mutate.
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  Speaker 2: As it regenerates in the host, it may mutate and
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  Speaker 2: regain its virulence, i.e. its ability to cause the severe, uh, uh,
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  Speaker 2: downstream effects of polio. Oh
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  Speaker 1: dear. And in this case, is that what we know
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  Speaker 1: that this poor infant received the oral form of the vaccine, i.e., um,
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  Speaker 1: the live attenuated form of polio, and is also immunocompromised.
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  Speaker 2: Based on the information that is out in the public domain, um,
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  Speaker 2: it looks as if this, this infant is 5 months old,
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  Speaker 2: received the first dose of the polio vaccine in the,
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  Speaker 2: in the oral form at 2 months, and then at
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  Speaker 2: 4 months, received the inactivated form, OK? Um, and then
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  Speaker 2: symptoms may have begun at about 4 months of age.
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  Speaker 2: So the question is whether or not.
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  Speaker 2: Uh, because of the immunocompromised state, the initial dose of
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  Speaker 2: the live vaccine may have, you know, reactivated and caused, uh, paralysis.
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  Speaker 1: Which form of the vaccine is utilized in Singapore for
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  Speaker 1: our
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  Speaker 1: children?
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  Speaker 2: And in Singapore since 2021, uh, we have already phased
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  Speaker 2: out the oral form of the vaccine. So, i.e., we
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  Speaker 2: no longer use the life attenuated virus form. So it's
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  Speaker 2: all injected now and it's the inactivated vaccine.
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  Speaker 1: OK, which still efficacious in terms of building up resistance
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  Speaker 1: to polio? Yeah,
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  Speaker 2: of
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  Speaker 2: course. Um, so both vaccines have, have a high level
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  Speaker 2: of efficacy, although in the past, 1 may have argued
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  Speaker 2: that the oral form may have been more immunogenic, so, i.e.,
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  Speaker 2: the amount of immune response that you get from the
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  Speaker 2: oral life form would have been slightly higher, but I
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  Speaker 2: think in general, the inactivated form, uh, for clinical purposes
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  Speaker 2: is highly effective.
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  Speaker 1: How rare is this, doctor, this idea of vaccine-related um development,
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  Speaker 1: vaccine associated polio developing?
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  Speaker 2: Um, well, if we're talking about paralysis as a result
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  Speaker 2: of polio from the, the vaccine, from the oral form
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  Speaker 2: of the vaccine, I think the recognized risk is about
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  Speaker 2: 1 in 2 million, so it's highly unlikely, but with
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  Speaker 2: an immunocompromised patient, um, you know, the, the risk is
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  Speaker 2: obviously much higher, but what we don't know is why
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  Speaker 2: this infant is immunocompromised, to what, to what degree of, of, uh.
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  Speaker 2: Uh, immune dysfunction this person has, and how did they
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  Speaker 2: discover it? Because obviously, the first dose was the oral form, i.e. the,
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  Speaker 2: the live virus was given.
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  Speaker 2: So clearly at 2 months, they may not have recognized
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  Speaker 2: the immunocompromised state of, of the patient.
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  Speaker 1: And it, it is possible that a parent might not
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  Speaker 1: know that their child is immunocompromised in some cases, is it?
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  Speaker 1: That's correct. OK, but that's a big umbrella term. Maybe
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  Speaker 1: if you can shoot out some examples of what we
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  Speaker 1: mean by the term immunocompromised because I mean, a listener
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  Speaker 1: might think it could be anything from
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  Speaker 1: Having asthma to having HIV. Do you know what I mean?
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  Speaker 1: So it's a very wide range.
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  Speaker 2: Yeah. Um, well, for adults, in general, uh, causes of,
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  Speaker 2: of poor immune system could include chemotherapy for cancer, somebody
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  Speaker 2: with advanced HIV infection, uh, if they're on, uh, high dose,
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  Speaker 2: high-dose steroids, for example, for lupus, OK.
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  Speaker 2: But for, for somebody who's 2 months old for an infant,
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  Speaker 2: it's likely that the cause of the, the immuno compromised
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  Speaker 2: state may have been an inherited immunodeficiency
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  Speaker 2: problem,
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  Speaker 1: something
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  Speaker 2: that they were speculating because we don't have that information,
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  Speaker 1: right, but that, but that is what we mean when
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  Speaker 1: somebody has an immunocompromised state, it means that therefore, um,
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  Speaker 1: it's affecting their own body's ability to respond to an infection. Correct.
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  Speaker 1: Got it.
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  Speaker 1: Now I wanna understand.
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  Speaker 1: There are many things, obviously, a lot of people are
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  Speaker 1: wondering like, oh my goodness, poor thing, this poor child,
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  Speaker 1: what's the, but then there's also a group of people
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  Speaker 1: asking questions, especially in the comment sections like, oh, does
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  Speaker 1: this mean that with one imported case of vaccine associated polio,
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  Speaker 1: that this somehow increases the risk of community transmission in
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  Speaker 1: any way? What do we know about that? Because as
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  Speaker 1: I mentioned in my introduction, was immediately um taken to
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  Speaker 1: NUH upon arrival and isolated upon admission. Obviously, our medical
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  Speaker 1: teams are wonderful and, and know their stuff and do
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  Speaker 1: their work very well. What is the risk of community infection?
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  Speaker 1: What do we know?
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  Speaker 2: Um, well, in relation to Singapore, I think that the
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  Speaker 2: risk of community transmission is, is virtually zero, and the
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  Speaker 2: reasons for this are several fold. Um, firstly, the patient
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  Speaker 2: was admitted directly into NUH, so I think, you know,
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  Speaker 2: the duration that this patient.
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  Speaker 2: May have been in, in, out in the open, potentially
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  Speaker 2: shading the virus to the community is negligible. Secondly, the
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  Speaker 2: family members were here only for a brief period before
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  Speaker 2: the diagnosis was made and then they were quickly isolated and,
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  Speaker 2: and screened as well. So again, um, the likelihood of
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  Speaker 2: them shedding the virus out in the community is unlikely.
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  Speaker 2: Thirdly, I think the level of sanitation in Singapore is
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  Speaker 2: first world, so it's again, uh, a factor in our favor. Um,
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  Speaker 2: and fourthly, um, as I said earlier, Singaporeans and Singapore
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  Speaker 2: residents are largely vaccinated against, uh, polio.
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  Speaker 1: Are there multiple shots required for polio vaccination? I forget actually.
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  Speaker 2: Well, in general, there, there are 5 for Singapore, but
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  Speaker 2: um other parts of the world may have only 4
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  Speaker 2: shots that are required, but in general, you would give
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  Speaker 2: it to infants at age.
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  Speaker 2: 2 months, 4, and 6 months, and then again at
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  Speaker 2: 18 months and then probably at the end of the
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  Speaker 2: primary school years at about 11 or 12 years old.
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  Speaker 2: Got it.
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  Speaker 1: OK. And the example that you mentioned of oral first
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  Speaker 1: followed by the uh non-oral version, that kind of combination
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  Speaker 1: approach is not practiced here in Singapore, right?
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  Speaker 2: No, that's that's not the norm. I suspect what happened
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  Speaker 2: is that the, the uh
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  Speaker 2: Infant probably got the oral form first, and then they
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  Speaker 2: realized that there may have been a problem with the,
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  Speaker 2: the patient's immunity, then they switched over to the inactivated
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  Speaker 2: form,
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  Speaker 1: potentially. Yes. Before we wrap up, let's spend a few
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  Speaker 1: minutes talking about what parents should be concerned about because
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  Speaker 1: I'm wondering whether the parents are reading the story, even
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  Speaker 1: though we've very clearly said how rare this case is
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  Speaker 1: and how the chances of it is something like 1
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  Speaker 1: in 2 million as you described earlier on.
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  Speaker 1: Should parents worry for their own kids' safety when taking
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  Speaker 1: the polio vaccine?
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  Speaker 2: Um, the form of polio vaccine that we use in
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  Speaker 2: Singapore is the inactivated form, so I would absolutely have,
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  Speaker 2: have no concerns there. Um, but on, on the flip side,
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  Speaker 2: I would be worried if a parent were to decide
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  Speaker 2: not to vaccinate their child because, you know, with, with
• 12:23
  Speaker 2: Singaporeans traveling for holidays for work, um, that you may
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  Speaker 2: come into contact with, with somebody shading the polio virus overseas.
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  Speaker 2: So it's important that you get vaccinated.
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  Speaker 2: And one of the things that I, I haven't mentioned
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  Speaker 2: earlier is that even though we think that wild type
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  Speaker 2: polio uh polio infections are largely eradicated in most parts
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  Speaker 2: of the world, um, one of the things that people
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  Speaker 2: don't know about is that, say in the last 18 months, OK,
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  Speaker 2: from early January 2023 up until the middle of 2024, uh,
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  Speaker 2: there have been multiple outbreaks of, of vaccine-derived um polio infections.
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  Speaker 2: So the WHO has recorded over 70 outbreaks.
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  Speaker 2: And
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  Speaker 1: that's more than 1 in 2 million risk that I'm, I'm,
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  Speaker 1: that seems to buck the trend of the 1 in
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  Speaker 1: 2 million.
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  Speaker 2: Uh, well, the, the, the outbreaks may not have led
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  Speaker 2: to paralysis, so essentially we're talking about people who have
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  Speaker 2: presented with uh a multitude of other symptoms that have
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  Speaker 2: been proven to be related to polio. So the reason
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  Speaker 2: for that really is because, um, um, all these countries
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  Speaker 2: would have relied on the oral form of the vaccine and.
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  Speaker 2: They would have had a lot of uh patients who
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  Speaker 2: are immunocompromised and continue to shed the virus as a
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  Speaker 2: result of getting the live virus. And because if the
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  Speaker 2: uptake within your community, within your country is low, then
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  Speaker 2: the risk obviously of an outbreak is going to be
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  Speaker 2: much
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  Speaker 2: higher.
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  Speaker 1: Would that not have contributed to the seesage, the cease
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  Speaker 1: of use of the oral version one would imagine?
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  Speaker 2: Um, not, not necessarily, because if you can imagine.
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  Speaker 2: The inactivated vaccine would, would require the patient to be
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  Speaker 2: injected with a vaccine. Um, so obviously that adds to
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  Speaker 2: one level of complexity in order to, to be able
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  Speaker 2: to roll out your vaccine compared to something like a
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  Speaker 2: liquid that you just pop into an infant's mouth.
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  Speaker 1: If you're talking about supply chains or chains to certain
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  Speaker 1: countries with lack of logistics or medical facilities, this all
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  Speaker 1: plays a part. Yeah.
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  Speaker 1: Got it. OK, final point, just a reiteration. I, I, I,
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  Speaker 1: I don't want people to start questioning something that's been
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  Speaker 1: around since 1978 and has served so much in terms
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  Speaker 1: of preventing disability and even death potentially from how serious
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  Speaker 1: polio was. Remind us why vaccination against polio remains our
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  Speaker 1: best events against a very serious illness.
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  Speaker 2: Well, it's got to do with, with uh risk-benefit uh
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  Speaker 2: uh ratios. So I think even though the risk whenever
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  Speaker 2: you acquire polio, the risk of you developing paralysis is low.
• 15:03
  Speaker 2: Um,
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  Speaker 2: But if you're unvaccinated, you're gonna put yourself, you know,
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  Speaker 2: at harm's way, um, in terms of the, of getting paralysis.
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  Speaker 2: And this paralysis is permanent. There's no treatment for it. Um,
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  Speaker 2: so once your arms or legs are disabled, you're, that's,
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  Speaker 2: that's you for life. And also the fact that it's
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  Speaker 2: life-threatening if it affects your, your, your uh nerves controlling
• 15:27
  Speaker 2: your breathing apparatus, then
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  Speaker 2: You know, we're gonna be in, in serious trouble that
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  Speaker 2: we cannot reverse.
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  Speaker 1: And it's easily transmissible as well, unfortunately. We cannot afford
• 15:36
  Speaker 1: a community outbreak and so it's wonderful that we do
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  Speaker 1: have in place um vaccination for everyone born after 1978.
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  Speaker 1: And that has played a big part in terms of
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  Speaker 1: keeping us polio-free to a large extent in Singapore. Doctor Chuu,
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  Speaker 1: it's been a pleasure. Thank you so much for speaking
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  Speaker 1: to my listeners today.
• 15:51
  Speaker 1: Thank you for having me on again. My guest on
• 15:53
  Speaker 1: the program, Doctor Nicholas Chou is an infectious diseases specialist
• 15:57
  Speaker 1: at Farrer Park Hospital. This has been Health Matters. I'm
• 15:59
  Speaker 1: Daniel Martin for CNA 938.
• 16:07
  Speaker 1: Before making any decisions based on the information in our program,
• 16:10
  Speaker 1: please consult a medical professional.