Interview: Could Covid-19 vaccination undo India’s hard-won battle against polio?

Exactly a decade ago, on January 13, 2011, India reported its last case of polio. Until the early 1990s, the highly infectious viral disease was hyperendemic in India. It resulted in an average of 500 to 1,000 children being paralysed every day. Scroll.in speaks to virologist Dr T Jacob John, the man behind the “pulse polio” campaign, on what it took to eradicate polio. The programme is seen as one of India’s biggest public health successes.

Take us through the early years of attempting universal vaccination, the particular challenges with the choice of polio vaccine. Did the lack of epidemiological tools of surveillance and reporting hamper initial efforts?

The World Health Organisation launched the Expanded Programme on Immunisation in 1974 to enable countries without public health and/or universal primary healthcare (such as India) to create a platform to deliver vaccines against six childhood diseases with high mortality and for which safe and effective vaccines were available.

[The] diseases were] childhood TB (vaccine BCG); diphtheria, pertussis, tetanus (vaccine DPT); measles (vaccine live attenuated measles vaccine) and polio (vaccine OPV). For neonatal tetanus, tetanus toxoid for pregnant women was included in EPI.

All these except OPV were extremely safe vaccines. OPV caused a rare case of paralytic polio in the vaccinated (Vaccine-Associated Paralytic Polio or VAPP) and also a rare case of paralytic polio in one or more contacts (Contact VAPP). Another completely safe vaccine against polio was available, namely Inactivated Polio Vaccine, but the EPI ignored it.

India adopted EPI in 1978 using all except the measles vaccine. Instead, the typhoid vaccine was included. In the mid-1980s, the typhoid vaccine was discontinued. In 1985, based on excellent public acceptance of the measles vaccine in Tamil Nadu, in a large-scale measles vaccine introduction by a joint Rotary and state government project, using a few million of Rotary-gifted measles vaccine, its roll out technically supervised by myself as a Rotarian-cum-virologist, the Seventh Planning Commission introduced it on a trial basis in 80 districts.

Thereafter each year 80 more districts were covered under the scheme until 1990 when the whole country came under measles vaccination and EPI was renamed Universal Immunisation Programme.

The Health Intelligence Bureau had been collecting data on various diseases through a “sentinel surveillance” scheme. The pre-EPI annual numbers of polio cases were less than 20,000 in 1979 and 1980, but it went up, paradoxically to 38,000 in 1981. Paradoxical because OPV was introduced in 1978-’79. Something was grossly wrong.

For eight consecutive years, annual polio remained above 20,000 and declined to below 20,000 in 1989. Now India had two problems with OPV – the well-known safety problem and the newly recognised efficacy problem. The government had a duty to monitor vaccine-associated paralytic polio, VAPP, but it did not. So the numbers of cases of VAPP in vaccinated and Contact VAPP were not counted, clearly contravening ethics of medicine. Between 100-200 probably developed VAPP annually – they were not informed or compensated.

In summary, during the first decade of EPI in India, 1978-1988, the problems of polio prevention were well known to EPI managers and ipso facto to the Directorate General of Health Service and Ministry of Health and Family Welfare and the government of India. The problems were both safety and efficacy. The alternate vaccine, IPV offered a way out of both problems. However, the government of India did not license IPV for importation.

EPI remains a vaccine delivery platform and not a disease control programme. This is partly the fault of the WHO EPI policy as a vaccine delivery platform and partly the fault of the Ministry of Health, which did not establish a policy to “control” the named diseases except for neonatal tetanus.

A modality called Public Health Surveillance is an integral part of any disease control. Establishing Public Health Surveillance, the essential tool in epidemiology to monitor disease control trajectory, is the first signal of the intention to control a disease. India still does not have Public Health Surveillance in spite of a workable model being available in India. When polio was targeted for eradication in 1988, the Ministry of Health knew the requirement of Public Health Surveillance but failed to establish one. Eventually WHO stepped in and established a vertical joint programme called National Polio Surveillance Project in 1997.

How did “pulse polio immunisation” came about in Vellore, evolving as a solution to low vaccine efficacy of the OPV. And what exactly is pulsing?

In the 1970s, we had documented many children not responding to OPV with antibody response. We were also observing children coming down with polio (lab confirmed) in spite of the recommended three doses of OPV. We were exploring various solutions to this problem.

One approach was to vaccinate large numbers of children simultaneously, instead of the age-based approach of three doses as children reached six, 10 and 14 weeks of age. A pilot study in a rural community showed that the approach was feasible. After two years of polio surveillance, documenting cases every month, average 4.2 cases per month, we vaccinated children in camps, one day each in October, November and December, 1981. The next nine months went without a single case.

Cases began to reappear in October, when the campaigns were repeated – in October, November and December 1982. Once again the population was polio-free for nine months. This method of periodic vaccination by campaign was called pulse vaccination.

In 1988, the World Health Assembly resolved to target polio for global eradication by the year 2000. You write that although India was a signatory, India’s efforts to implement it started on a national level only in 1995-1996. What was happening in the interim to India’s polio vaccination efforts?

The WHA resolution was to eradicate polio using the EPI platform and polio vaccines. The WHO probably expected India to strengthen its Universal Immunisation Programme and streamline polio vaccination – but that did not materialise.

In 1987, the government had decided to establish an IPV manufacturing facility in Manesar. It was closed in 1992. So, India had to try to eradicate polio using only OPV.

In 1995, the Delhi Government undertook a pulse polio vaccination campaign and demonstrated the feasibility of upscaling pulse vaccination. There was no polio surveillance anywhere except in the North Arcot District in which we were working to control polio. In 1997, the National Polio Surveillance Project was established and polio surveillance began nation-wide. That is when the Universal Immunisation Programme, the government of India and the WHO realised that three doses of OPV were not protecting children against polio. When 2000 dawned, polio had not been eradicated.

Take us through the introduction of the National Pulse Polio Immunisation programme in 1995 and how it progressed through to the year 2000, which was the initial target year for polio eradication.

In 1999, the wild poliovirus type 2 was interrupted in Uttar Pradesh, the last stronghold in the world. That proved, finally, that sufficient vaccine coverage had been reached to eradicate the one virus type against which vaccine efficacy of trivalent OPV was highest.

Post-2000, everyone realised that even 90%-95% of three-dose OPV coverage achieved through routine OPV plus pulse vaccination was insufficient to interrupt types 1 and 3 poliovirus transmission in the States of Uttar Pradesh and Bihar. That was when the polio eradication leadership understood that the density of under-five children was a formidable barrier to polio eradication. Uttar Pradesh and Bihar were most affected because of high population density plus high birth rate. Kerala and West Bengal had high population density but much lower bath rates.

In 1976 I published a study in the Bulletin of WHO, showing that monovalent OPV types 1 and 3 had two-and-half times higher efficacy than trivalent OPV. Based on that study, an application was made, and the Drugs Controller General of India approved the use of monovalent OPV types 1 and 3. During 2006 through 2010 monovalent OPV type 1 was used and thus wild virus type 1 was eradicated, soon followed by type 3 also, helped by bivalent OPV containing types 1 and 3.

Many have said that the continued use of OPV after the eradication of Wild Polio is ethically unacceptable, given evidence of the rare adverse event of Vaccine-Associated Paralytic Polio. The government has of course not released any data on VAPP. Why are VAAP cases not classified as polio? Shouldn’t they be?

While India and other countries like Egypt, Nigeria, Pakistan and Afghanistan were struggling with the low vaccine efficacy of OPV, governments were not paying attention to the problem of vaccine viruses causing polio (VAPP). Under the very nose of the global polio eradication programme, the vaccine virus type 2 began circulating in African countries and causing polio outbreaks. This virus is called circulating vaccine-derived poliovirus type 2 (cVDPV-2).

In 2000 there were 139 cases of polio due to wild poliovirus type 1 in Afghanistan and Pakistan but there were 910 polio cases caused by the vaccine-derived virus. This is highly problematic, as no public health program has any right to do such large scale harm to children in 25 countries in Africa.

What is Non Polio AFP or NPAFP? Is this different from VAAP?

AFP is acute flaccid paralysis, the clinical presentation of polio. Not all cases of AFP are polio – hence virological confirmation is resorted to diagnose and count polio. VAPP is also AFP, but the virus in children with VAPP will be vaccine virus and not wild virus. Since most children given OPV will also show vaccine poliovirus in the stool, VAPP is quietly called non-polio AFP, a highly questionable practice.

Why do we continue annual pulse polio immunisation, in spite of the certification that India is polio-free?
Keeping coverage very high is to prevent type 1 from becoming circulating vaccine-derived poliovirus type 2 or cVDPV-2.

The government has issued a notification declaring that the polio national immunisation drive scheduled from January 17 will be indefinitely postponed in light of the upcoming Covid-19 vaccination. What problem do you envisage?

If we skip the pulse polio drive, the risk is the development of circulating vaccine-derived poliovirus type 1. Postponing the drive to February or March may be sufficient [to serve the purpose of launching Covid-19 vaccination drive], but, yes even that poses a small risk..

Smitha Nair is a journalist in Mumbai.