Search

The incidence of polio has decreased by more than 99.9% and currently, only two countries are endemic for wild poliovirus. However, increasing outbreaks of circulating vaccine-derived poliovirus globally in the last few years, with the latest ones in high-income, exclusive inactivated polio virus vaccine (IPV)-using countries have brought out a new dimension to the end game of polio eradication. The inability of the current IPV to induce efficient mucosal immunity in the intestine is likely to be one of the key reasons behind the silent transmission of the polio virus in these countries. New challenges demand concerted global efforts with renewed vigor to cross the last mile. We need to aggressively cover up areas of under-vaccination and continue large-scale genomic surveillance. Further, the availability of a novel oral polio vaccine (nOPV2), and the likely availability of Sabin IPV and a more refined IPV with mucosal adjuvant in the near future is likely to go a long way in achieving this remarkable feat.

Global Polio Eradication and Endgame Strategic Plan 2013-18 calls for the ultimate withdrawal of oral polio vaccines (OPV) from all immunization programs across the world. The phased globally synchronized withdrawal would begin with type 2 serotype in 2016 through a switch from trivalent OPV (tOPV) to bivalent OPV (bOPV) and is associated with small but real risk of Vaccine Derived Polio Virus (VDPV) outbreaks. To mitigate this risk, efforts across the world, including India, are underway that comprise of Inactivated Polio Vaccine (IPV) introduction, containment of type 2 wild and vaccine strains, securing bOPV supplies, and surveillance and response protocols for any outbreaks after switch. Switch implementation in India is particularly challenging as country has one of the largest cold chain system in world with - 27000 cold chain points from where tOPV will be exchanged with bOPV and disposed in short time frame as any use/storage of tOPV beyond switch will jeopardize the global polio eradication.

Objective: In March 2014, India, the country with historically the highest burden of polio, was declared polio free, with no reported cases since January 2011. We estimate the health and economic benefits of polio elimination in India with the oral polio vaccine (OPV) during 1982-2012., Methods: Based on a pre-vaccine incidence rate, we estimate the counterfactual burden of polio in the hypothetical absence of the national polio elimination program in India. We attribute differences in outcomes between the actual (adjusted for under-reporting) and hypothetical counterfactual scenarios in our model to the national polio program. We measure health benefits as averted polio incidence, deaths, and disability adjusted life years (DALYs). We consider two methods to measure economic benefits: the value of statistical life approach, and equating one DALY to the Gross National Income (GNI) per capita., Results: We estimate that the National Program against Polio averted 3.94 million (95% confidence interval [CI]: 3.89-3.99 million) paralytic polio cases, 393,918 polio deaths (95% CI: 388,897- 398,939), and 1.48 billion DALYs (95% CI: 1.46-1.50 billion). We also estimate that the program contributed to a $1.71 trillion (INR 76.91 trillion) gain (95% CI: $1.69-$1.73 trillion [INR 75.93-77.89 trillion]) in economic productivity between 1982 and 2012 in our base case analysis. Using the GNI and DALY method, the economic gain from the program is estimated to be $1.11 trillion (INR 50.13 trillion) (95% CI: $1.10-$1.13 trillion [INR 49.50-50.76 trillion]) over the same period., Conclusion: India accrued large health and economic benefits from investing in polio elimination efforts. Other programs to control/eliminate more vaccine-preventable diseases are likely to contribute to large health and economic benefits in India.

Objective: To assess the seroprevalence against all three poliovirus serotypes in traditional high risk areas in Bihar, lowest routine immunization coverage areas in Madhya Pradesh and migrant population living in Mumbai urban slums., Design: Cross-sectional Survey., Setting: Subjects selected by house to house visit (community based) and transported to government health facilities for further study procedures., Participants: 1137 randomly selected healthy infants 6-11 months of age residing in the selected high-risk areas., Methods: Serum samples from the study site were shipped to Enterovirus Research Centre (ERC), Mumbai to determine the neutralizing antibodies against all three poliovirus serotypes. Children with a reciprocal antibody titer ≥1:8 were considered seropositive to the specific poliovirus., Results: Overall, seroprevalence in all the three study areas was 98%, 98% and 91% against poliovirus type-1, type-2 and type-3, respectively. Bihar had a seroprevalence of 99%, 99% and 92% against type-1, type-2 and type-3 respectively. Corresponding figures for Madhya Pradesh and Mumbai were 98%, 99% and 88% and 98%, 97% and 94%, respectively., Conclusion: The study found high seroprevalence against all three poliovirus types not only in the traditional high-risk areas for polio in India, but even in the areas known to have low routine immunization coverage and among the migratory clusters living in Mumbai urban slums. Type-2 seroprevalence was found to be high. These findings are reassuring against the threat of emergence of circulating vaccine derived polioviruses (cVDPVs) in the country subsequent to switch from trivalent oral polio vaccine to bivalent oral polio vaccine in the routine immunization schedule from April 2016.

Objective: IgG and IgA immunocompetence of children with wild poliovirus poliomyelitis and non-polio acute flaccid paralysis., Methods: 932 cases of acute flaccid paralysis, reported in 2008-2009, were tested for presence of polio and non-polio enteroviruses according to the WHO standards. Serum IgA and IgG levels were determined by sandwich ELISA., Results: Mean (SD) IgA levels [0.87 (0.62)g/L; n=28] of virologically confirmed poliomyelitis cases were lower than those of virus negative [1.21 (0.83)g/L; n=612] and non-polio Enterovirus positive [1.22 (0.79)g/L; n=240] cases of acute flaccid paralysis. No significant difference was observed in the concentration of IgG among these groups., Conclusions: IgA plays an important role in protection against poliomyelitis.

The diagnosis of polio dependents on culturing the virus in stool samples of children with AFP. Using data obtained under the "Right to Information Act" of instances where only one of the two samples was positive for polio, it was possible to estimate the sensitivity of the system to detect cases of polio. The calculations suggest that there were 1625 (95% CI 1528 to 1725) cases of polio in India in 2006 rather than the 674 reported widely!

This cross sectional study was performed in a tertiary level teaching hospital to evaluate and compare the antibody levels in children below 6 years who had received oral polio vaccination through Pulse Polio Immunization (PPI) with those children who had received both routine immunization as well as PPI. Detail history of polio immunization was taken. Serum samples were then collected for antibody determination by neutralization tests with standard polio viruses using Vero cell lines. Total 400 children were studied; 14 were found unvaccinated. Out of the remaining 386 (96.5%) vaccinated children, 292 (75%) had received both routine and pulse polio immunization, 68 (17%) had only PPI while 26 (6.7%) had received only routine immunization. The seropositivity was lowest for P3 and highest for P2. Overall seroprevalence for PI, P2 and P3 in vaccinated children was 89.1%, 93% and 80.6% respectively, and did not differ significantly between the three vaccinated subgroups. However, children who were immunized by both routine and PPI had higher geometric mean titers (315.5, 484.7 and 187.4 for PI, P2 and P3 respectively) when compared with those who had received only PPI (P<0.001 for each PI, P2 and P3), as well as those who had received only routine immunization with OPV (P<0.05 for PI, p<0.001 for P2, and P<0.01 for P3). Despite the reasonable immunization coverage in study population, there were 29 (7.25%) triple negative cases. Hence other causes of low seroconversion should also be considered to achieve polio free India.

Objective: To describe the epidemiological characteristics of poliomyelitis in Delhi in 1997 after four consecutive statewide immunization campaigns with oral polio vaccine (OPV)., Methods: Stool samples were collected from 158 cases of acute flaccid paralysis (AFP) along with their age, sex, residential address, immunization history and dates of onset of paralysis, reporting and investigation. The samples were processed for isolation of polioviruses. In addition, historical data on vaccination coverage surveys and OPV testing were reviewed. These data were analyzed to understand the epidemiological patterns of poliomyelitis in Delhi., Results: Of 158 cases of AFP, about 23% were investigated within 2 days of onset of paralysis. Two samples each were collected from 97 (61%) cases, and one each from the remaining cases. Detection of 158 cases of AFP gave an incidence of 1.34 per 100,000 population. About 36% (57/158) of AFP cases excreted poliovirus, mostly (53/158) wild poliovirus. Of the wild poliovirus isolates, 72% (38/53) and 25% (13/53) were serotypes P1 and P3 respectively; 2 isolates were P2. Almost 95% (146/154) of AFP cases and all the laboratory confirmed cases (excreting wild poliovirus) occurred in children below 5 years of age. Only one-third of AFP (55/158) or laboratory confirmed cases (18/53) had received 3 or more doses of OPV before onset of paralysis. About one-fourth of cases in both the categories were totally unvaccinated. AFP cases occurred round the year but peaked in November-December. Peaks were always observed during July-August in the past. The cases were widely scattered without any obvious clustering in any locality., Conclusions: Poliomyelitis has declined substantially in Delhi. The study underscores the need for further efforts to improve vaccine coverage levels, AFP surveillance, and cold chain maintenance to achieve the complete interruption of transmission.

Objective: To estimate the sensitivity of poliomyelitis surveillance in India., Design: A comparison of two sets of data obtained from lameness surveys and routine surveillance system., Methods: Lameness surveys were undertaken by the Ministry of Health and Family Welfare in 1981, 1989 and 1992 using 30-cluster sampling technique. These data were compared with the number of polio cases reported through routine surveillance system., Results: Based on the 1981 survey which was undertaken near the initiation of routine immunization with oral polio vaccine (OPV) in India, poliomyelitis incidence was estimated at 25 cases per 100,000 population. Subsequent studies in 1989 and 1992 estimated a decrease in incidence rates to 15.7 and 6.3 cases per 100,000 population, respectively. Comparing the number of reported cases with the survey estimates provided a measure of the sensitivity of (completeness of reporting) surveillance; the sensitivity increased from 8% in 1981, to 20% in 1989, to 32% in 1992., Conclusion: The results are encouraging when compared with the global estimates of 10% reporting in 1993. Nevertheless, there is a need for further improvement in the completeness of reporting of poliomyelitis cases to detect all the cases of acute flaccid paralysis to allow epidemiological investigations and effective follow-up action which is critical to interrupt wild virus transmission.

Objective: To study the trends of paralytic poliomyelitis in pre Pulse Polio Immunization period., Setting: Hospital based sentinel surveillance., Methods: Analysis of 6704 line-listed poliomyelitis cases from January 1989 to December 1994 attending the Department of Physical Medicine and Rehabilitation., Results: 85% of all cases reported in Delhi were from this center. A decline in alternate year peaks was observed from 1621 cases in 1990 to 1062 cases in 1994. There was an increase in proportion of cases with poliomyelitis in fully vaccinated children from 14% to 22.9%. Polio type I virus was the commonest isolated virus in all the years except 1993, when type II was isolated in 38.7% of cases., Conclusion: Despite improvement in immunization coverage, the study reveals that a large number of children (67.2%) who suffer from poliomyelitis are unvaccinated. This stresses need to intensify and sustain high level of immunization coverage with effective vaccine.

Due to lacunae in coverage and limitation in efficacy, immunization with oral polio vaccine has left a group of susceptible children at risk of developing poliomyelitis. The present study, with the help of statistics, projects the size of that susceptible pool of underfive children in Delhi during 1995. With the help of available data and some assumption, a formula has been developed for the purpose. The size of the pool thus estimated is about 3.7 lakh. There is a need to develop methodology for finding such susceptibles at community level, particularly at the terminal phase of eradication. An additional approach of immunization has also been suggested to facilitate the prospect of polio eradication.

An outbreak of poliomyelitis that occurred in the year 1992 in Telangana region of Andhra Pradesh, South India was investigated to understand the reasons for persistence of poliomyelitis in the general population and for the outbreak in Andhra Pradesh in particular. The study comprised of a detailed investigation of epidemiological and clinical features, serology and vaccination status and a case control study to calculate vaccine efficacy by matched pair analysis. The outbreak occurred after a relative quiescence of 3 years. The age group of the patients ranged from 2 months to 5 years, 26.5% being infants and 70.2% being children between 1 and 5 years. The outbreak was mainly caused by Type 1 poliovirus. Vaccine efficacy was found to be 70%. Antibody response was not high in cases. Seventy six per cent of the children with poliomyelitis were unvaccinated. Ignorance of the mothers and family interference were the main causes for not vaccinating the children. The study indicates the need to increase the vaccination coverage and inclusion of children upto 5 years in the programme. Absence of vaccination is the major risk factor for the outbreak. The persistence of poliomyelitis in older children, low antibody response and suboptimal vaccine efficacy point out the problem of achieving control with OPV in tropical countries and suggest the need for alternate strategies. Better health education strategies need to be developed.