Concurrent outbreaks of circulating vaccine-derived poliovirus serotypes 1 and 2 (cVDPV1, cVDPV2) were confirmed in the Republic of the Philippines in September 2019 and were subsequently confirmed in Malaysia by early 2020. There is continuous population subgroup movement in specific geographies between the two countries. Outbreak response efforts focused on sequential supplemental immunization activities with monovalent Sabin strain oral poliovirus vaccine type 2 (mOPV2) and bivalent oral poliovirus vaccines (bOPV, containing Sabin strain types 1 and 3) as well as activities to enhance poliovirus surveillance sensitivity to detect virus circulation. A total of six cVDPV1 cases, 13 cVDPV2 cases, and one immunodeficiency-associated vaccine-derived poliovirus type 2 case were detected, and there were 35 cVDPV1 and 31 cVDPV2 isolates from environmental surveillance sewage collection sites. No further cVDPV1 or cVDPV2 have been detected in either country since March 2020. Response efforts in both countries encountered challenges, particularly those caused by the global COVID-19 pandemic. Important lessons were identified and could be useful for other countries that experience outbreaks of concurrent cVDPV serotypes.
The Virology Division in the Institute for Medical Research, Kuala Lumpur, Malaysia performs potency tests on oral polio vaccines and live attenuated measles vaccines. Since these potency tests were introduced in 1981 a total of 752 tests have been performed on vaccine samples from peripheral immunization centers. Of 165 representative vaccine samples sent for potency evaluation after a cold chain breakdown 154 (87%) passed minimum potency requirements recommended for immunization of infants. In the absence of potency evaluation, those vaccines exposed to temperatures higher than the recommended storage range would be discarded, perhaps resulting in unnecessary wastage and economic loss. Results of the vaccine potency evaluation has enabled health authorities to indirectly monitor cold chain efficiency and ensure the high quality of viral vaccines used in our childhood immunization program.
Paralytic poliomyelitis is a constantly rising problem in the developing world. It may take an insiduous endemic "infantile paralysis" behaviour exacting a high toll in the first few years of life, as in Ghana or Burma but on the other hand it may take the form of sudden extensive outbreaks of paralytic disease as in Argentina, Mexico or Malaysia. The developed world has controlled the disease by effectively immunizing a very high proportion of their populations, but those who have not been vaccinated are at risk even in countries with very high coverage, as has been noted in the Netherlands, Sweden, United States of America, etc. There is no reason to have a crippled paralytic child (or adult). Both the live and killed vaccines have been repeatedly shown to be safe and effective. The minute risk incidental to vaccination is more than one hundredfold smaller than the risk from the disease, not only in the developing world but in the developed world as well. Therefore, the question of which vaccine to use is of far less relevance than of how to increase effective coverage with any available vaccine. This does not mean that vaccine control should be relaxed. A health respect should be maintained for the polioviruses used as vaccine sources and great care must be exercised by those undertaking the manufacture or the administration of vaccine.
Since 1992, surveillance for acute flaccid paralysis (AFP) cases was introduced in Malaysia along with the establishment of the National Poliovirus Laboratory at the Institute for Medical Research. In 2008, the Ministry of Health, Malaysia, approved a vaccine policy change from oral polio vaccine to inactivated polio vaccine (IPV). Eight states started using IPV in the Expanded Immunization Programme, followed by the remaining states in January 2010. The objective of this study was to determine the viral aetiology of AFP cases below 15 years of age, before and after vaccine policy change from oral polio vaccine to inactivated polio vaccine. One hundred and seventy-nine enteroviruses were isolated from the 3394 stool specimens investigated between 1992 and December 2012. Fifty-six out of 107 virus isolates were polioviruses and the remaining were non-polio enteroviruses. Since 2009 after the sequential introduction of IPV in the childhood immunization programme, no Sabin polioviruses were isolated from AFP cases. In 2012, the laboratory AFP surveillance was supplemented with environmental surveillance with sewage sampling. Thirteen Sabin polioviruses were also isolated from sewage in the same year, but no vaccine-derived poliovirus was detected during this period.
The World Health Organisation Western Pacific Region countries were declared free of polio in 2000 until a polio outbreak involving 305 cases occurred in Indonesia in 2006. It was not until 2014 that the World Health Organisation South East Asia region was officially declared polio-free again. However, in February 2019, the Global Polio Eradication Initiative announced a new circulating vaccine-derived poliovirus outbreak in the Papua province of Indonesia. To make matter worse, the outbreak responses were tardy and led to transmission among migrating communities to other cities. The pressing regional issues of polio outbreak caused by circulating vaccine-derived poliovirus and use of oral polio vaccine have not been well presented. Our letter highlighted the suboptimal outbreak responses as well as the necessity of cross-border vaccination to curb continued poliovirus transmission.
The Institute for Medical Research, Malaysia, was designated the National Reference Laboratory for Poliomyelitis Eradication (NRLPE) in 1992. Since then, our Polio Laboratory has collaborated actively with the Disease Control Division, Ministry of Health (MOH), Malaysia and WHO towards achieving polio eradication. Since 1992, the NRLPE has investigated 1,063 stool specimens from 641 acute flaccidparalysis (AFP) cases. One hundred and one enteroviruses were isolated from these specimens. Positive cell cultures were confirmed by microneutralization assay using standard WHO antisera. All enterovirus isolates were sent to the Victorian Infectious Disease Reference Laboratory in Melbourne, Australia, for further identification and poliovirus intratypic differentiation. Thirty-one out of these 101 virus isolates (30%) were polioviruses (PV) and the remaining 70 (70%) were non-polio enteroviruses (NPEV) which included coxsackie B viruses, echoviruses and enterovirus 71. Three of the poliovirus isolates were wild-type polioviruses isolated in 1992 which were the last wild-type polioviruses isolated in Malaysia. The rest were vaccine-related Sabin-like strains. Monthly reports of the virological investigation of AFP cases are sent to WHO and to the MOH, AFP control committee. The NRLPE continues to play an integral role in AFP surveillance and is committed to the WHO's goal of global polio eradication by the year 2005.
Stool samples from healthy children mainly of the low income group aged 0 to 7 years of age from five Maternal and Child Health Centres in Kuala Lumpur were obtained for isolation of enteroviruses. The specimens were collected before and after the mass vaccination given in the face of polio type 1 epidemic which started in October, 1971. The prevelance rate of enteroviruses was 11.9% (3.0% polioviruses, 8.9% non-polio enteroviruses) before the vaccination and essentially the same after. Coxsackie A viruses predominated over the other enteroviruses in the pre- and post-vaccination phases. The highest isolation rate of enteroviruses was observed in children 0 to 2 years age. No significant differences in distribution by sex, race and month were noted. A sharp fall in the prevalence rates of total enteroviruses and polioviruses was noted shortly after the mass vaccination campaign However, the rates reverted to the pre-vaccination state during the next successive years.
A qualitative study design was adapted to explore the challenges faced by health workers (HWs) during the polio health campaign. In addition, HWs' opinions about the factors causing parents to refuse oral polio vaccination (OPV) were also explored. Four focus group discussions (FGDs) were held (from 1st January 2015-31st March 2015) with the HWs who participated in the OPV campaigns in the polio red zones of Khyber Pakhtoon Khawa (KPK) province of Pakistan, namely Kohat (FG 1), Domel and Bannu (FG 2), Hangoo (FG 3), and Peshawar (FG 4). A total of N=42 HWs (10-11 in each FG) agreed to participate in this study. Overall, HWs disclosed that public attitude and harsh behaviour towards the HWs and security threats are the two main challenges they face. Common issues hindering parents' willingness to vaccinate their children against OPV are: OPV is seen as haram and not permitted in Islam, it is said to contain the blood of pigs (Khinzir) and monkeys, and parents are afraid that it is done to induce sterility among their children. HWs also shared that parents have a strong belief in the conspiracies that are associated with OPV, i.e. the USA and CIA, are spying on us and our government is helping them to achieve their agenda. Furthermore, HWs revealed that frequent visits may further strengthen parents' perceptions and make them more resistant to OPV. The common side effects of OPV reported by parents were mainly gastro-intestinal problems and in some cases mild to moderate fever with some respiratory symptoms. There is a great need to improve the logistics and facilities for HWs assisting in vaccination programmes. Furthermore, it is necessary to improve education, so people understand the basic concept of revaccination and booster doses, thereby assisting in creating a basic understanding of vaccinations, which may trigger changes in attitudes and make people believe in the benefits of OPV rather than following the conspiracies that lead them to refuse it.