Inactivated Polio Vaccine Research Articles

Maximising the impact of inactivated polio vaccines

Maximising the impact of inactivated polio vaccines

Nonspecific Effects of Oral Polio Vaccine on Diarrheal Burden and Etiology Among Bangladeshi Infants

As the global polio eradication initiative prepares to cease use of oral polio vaccine (OPV) in 2020, there is increasing interest in understanding if oral vaccination provides non-specific immunity to other infections so that the consequences of this transition can be effectively planned for and mitigated. Data were collected from infants in an urban slum in Bangladesh (Mirpur, Dhaka) as part of the performance of rotavirus and oral polio vaccines in developing countries (PROVIDE) study. Following vaccination with trivalent oral polio vaccine (tOPV) at 6, 10, and 14 weeks, infants were randomly assigned to receive tOPV (n = 315) or inactivated polio vaccine (IPV) (n = 299) at 39 weeks. Episodes of diarrhea were documented through clinic visits and twice-weekly house visits through 52 weeks. In sum, 14 pathogens associated with diarrhea were analyzed with TaqMan Array Cards. Although the proportion of children experiencing diarrhea was not different between the tOPV and IPV groups (P = .18), the number of days with diarrhea (P = .0037) and the number of separate diarrheal episodes (P = .054) trended lower in the OPV arm. Etiological analysis revealed that male tOPV recipients were less likely to have diarrhea of bacterial etiology (P = .0099) compared to male IPV recipients but equally likely to experience diarrhea due to viruses (P = .57) or protozoa (P = .14). Among the 6 bacterial enteric pathogens tested, only Campylobacter jejuni/coli detection was significantly reduced in the OPV arm (P = .0048). Our results suggest that OPV may cause nonspecific reductions in mortality, as has been studied elsewhere, by reducing etiology-specific diarrheal burden. This is likely driven by reductions in bacterial diarrhea. Further study of nonspecific OPV effects before global cessation is supported. NCT01375647.

Intranasal and sublingual delivery of inactivated polio vaccine

Polio is on the brink of eradication. Improved inactivated polio vaccines (IPV) are needed towards complete eradication and for the use in the period thereafter. Vaccination via mucosal surfaces has important potential advantages over intramuscular injection using conventional needle and syringe, the currently used delivery method for IPV. One of them is the ability to induce both serum and mucosal immune responses: the latter may provide protection at the port of virus entry.The current study evaluated the possibilities of polio vaccination via mucosal surfaces using IPV based on attenuated Sabin strains. Mice received three immunizations with trivalent sIPV via intramuscular injection, or via the intranasal or sublingual route. The need of an adjuvant for the mucosal routes was investigated as well, by testing sIPV in combination with the mucosal adjuvant cholera toxin.Both intranasal and sublingual sIPV immunization induced systemic polio-specific serum IgG in mice that were functional as measured by poliovirus neutralization. Intranasal administration of sIPV plus adjuvant induced significant higher systemic poliovirus type 3 neutralizing antibody titers than sIPV delivered via the intramuscular route. Moreover, mucosal sIPV delivery elicited polio-specific IgA titers at different mucosal sites (IgA in saliva, fecal extracts and intestinal tissue) and IgA-producing B-cells in the spleen, where conventional intramuscular vaccination was unable to do so. However, it is likely that a mucosal adjuvant is required for sublingual vaccination. Further research on polio vaccination via sublingual mucosal route should include the search for safe and effective adjuvants, and the development of novel oral dosage forms that improve antigen uptake by oral mucosa, thereby increasing vaccine immunogenicity. This study indicates that both the intranasal and sublingual routes might be valuable approaches for use in routine vaccination or outbreak control in the period after complete OPV cessation and post-polio eradication.

Safety of Tetanus, Diphtheria, and Pertussis Vaccination During Pregnancy: A Systematic Review.

To assess antenatal, birth, and infant outcomes for pregnant women, fetuses, and infants after antenatal vaccination with any antigen present in combination pertussis vaccines. PubMed, EMBASE, Literature in the Health Sciences in Latin America and the Caribbean, ClinicalTrials.gov, Cochrane Library, and World Health Organization (inception to May 5, 2016). Studies reporting outcomes for pregnant women, their fetus, or infant after antenatal exposure to either monovalent or combined tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) or inactivated polio vaccines were considered for inclusion. A total of 21 studies were included in this review. Point estimates ranged from 0.47 to 1.50 for preterm birth (less than 37 weeks of gestation), 0.65-1.00 for small for gestational age (birth weight less than the 10th percentile), 0.36-0.85 for stillbirth, 0.16-1.00 for neonatal death, 0.76-1.20 for low birth weight (less than 2,500 g), and 0.20-0.91 for congenital anomalies. All lower 95% confidence intervals (CIs) were less than 1.0. Of three retrospective studies assessing chorioamnionitis after vaccination, one showed a small but statistically significant increase. Point estimates for all anomalies after antenatal tetanus toxoid vaccination ranged from 1.20 to 1.60 and had 95% CIs that crossed 1.0. There was substantial clinical and methodologic heterogeneity from mainly retrospective observational studies with an overall high risk of bias. Objective rates of fever were low, 3% or below, and more common systemic events observed included headache, malaise, and myalgia. Evidence suggests that antenatal combined Tdap administered during the second or third trimester of pregnancy is not associated with clinically significant harms for the fetus or neonate. Medically attended events in pregnant women are similar between vaccinated and unvaccinated groups.

Effect of stepwise perinatal immunization education: A cluster-randomized controlled trial

BackgroundPerinatal immunization education is important for improving the immunization outcomes of infants; however, the content of educational materials used at each perinatal period has not been carefully evaluated. We hypothesized that stepwise education offered at different perinatal periods would improve infant immunization status and enhance maternal immunization knowledge. MethodsIn this cluster-randomized controlled trial, pregnant women were recruited from nine obstetric sites in Niigata, Japan. The intervention group received a stepwise, interactive education intervention (prenatally, postnatally, and 1month after birth). The control group received a leaflet containing general information on immunization. Infant immunization status was evaluated at 6months of age, and maternal immunization knowledge was evaluated by a written survey after each intervention. ResultsAmong 188 study participants, 151 (80.3%) replied to the final post-intervention survey. At 6months of age, the percentage of children who completed three doses of inactivated polio, diphtheria, tetanus toxoid, and acellular pertussis (DTaP-IPV) vaccine was higher in the intervention group than in the control (p=0.04); however, no differences between groups were observed for the Haemophilus influenzae type b (Hib) (p=0.67) or 13-valent pneumococcal conjugate (PCV13) vaccines (p=0.20). The duration to the completion of the third dose of the DTaP-IPV, Hib, and PCV13 vaccines was shorter in the intervention group than in the control (p=0.03, p<0.01, and p<0.01, respectively). Furthermore, maternal knowledge scores exhibited significantly greater improvement in the intervention group over time compared with those of the control group (p=0.02). ConclusionsStepwise perinatal immunization education improved immunization schedule adherence for required vaccines and improved maternal immunization knowledge.

Oral polio vaccine plus inactivated polio vaccine versus oral polio vaccine alone for reducing polio in children under two years of age

Reason for withdrawal from publication The Cochrane Developmental, Psychosocial and Learning Problems Editorial Team have withdrawn this protocol as it was published more than three years ago.

Long-term evaluation of mucosal and systemic immunity and protection conferred by different polio booster vaccines.

Oral polio vaccine (OPV) and Inactivated Polio Vaccine (IPV) have distinct advantages and limitations. IPV does not provide mucosal immunity and introduction of IPV to mitigate consequences of circulating vaccine-derived polio virus from OPV has very limited effect on transmission and OPV campaigns are essential for interrupting wild polio virus transmission, even in developed countries with a high coverage of IPV and protected sewer systems. The problem is magnified in many countries with limited resources. Requirement of refrigeration for storage and transportation for both IPV and OPV is also a major challenge in developing countries. Therefore, we present here long-term studies on comparison of a plant-based booster vaccine, which is free of virus and cold chain with IPV boosters and provide data on mucosal and systemic immunity and protection conferred by neutralizing antibodies.Mice were primed subcutaneously with IPV and boosted orally with lyophilized plant cells containing 1 μg or 25 μg polio viral protein 1 (VP1), once a month for three months or a single booster one year after the first prime. Our results show that VP1-IgG1 titers in single or double dose IPV dropped to background levels after one year of immunization. This decrease correlated with >50% reduction in seropositivity in double dose and <10% seropositivity in single dose IPV against serotype 1. Single dose IPV offered no or minimal protection against serotype 1 and 2 but conferred protection against serotype 3. VP1-IgA titers were negligible in IPV single or double dose vaccinated mice. VP1 antigen with two plant-derived adjuvants induced significantly high level and long lasting VP1-IgG1, IgA and neutralizing antibody titers (average 4.3–6.8 log2 titers). Plant boosters with VP1 and plant derived adjuvants maintained the same level titers from 29 to 400 days and conferred the same level of protection against all three serotypes throughout the duration of this study. Even during period, when no plant booster was given (∼260 days), VP1-IgG1 titers were maintained at high levels. Lyophilized plant cells expressing VP1 can be stored without losing efficacy, eliminating cold chain. Virus-free, cold-chain free vaccine is ready for further clinical development.

The polio endgame: rationale behind the change in immunisation

The decades long effort to eradicate polio is nearing the final stages and oral polio vaccine (OPV) is much to thank for this success. As cases of wild poliovirus continue...

Guidance for Assessment of Poliovirus Vaccination Status and Vaccination of Children Who Have Received Poliovirus Vaccine Outside the United States.

In 1988, the World Health Assembly resolved to eradicate poliomyelitis (polio). Since then, wild poliovirus (WPV) cases have declined by >99.9%, from an estimated 350,000 cases of polio each year to 74 cases in two countries in 2015 (1). This decrease was achieved primarily through the use of trivalent oral poliovirus vaccine (tOPV), which contains types 1, 2, and 3 live, attenuated polioviruses. Since 2000, the United States has exclusively used inactivated polio vaccine (IPV), which contains all three poliovirus types (2,3). In 2013, the World Health Organization (WHO) set a target of a polio-free world by 2018 (4). Of the three WPV types, type 2 was declared eradicated in September 2015. To remove the risk for infection with circulating type 2 vaccine-derived polioviruses (cVDPV), which can lead to paralysis similar to that caused by WPV, all OPV-using countries simultaneously switched in April 2016 from tOPV to bivalent OPV (bOPV), which contains only types 1 and 3 polioviruses (5). This report summarizes current Advisory Committee on Immunization Practices (ACIP) recommendations for poliovirus vaccination and provides CDC guidance, in the context of the switch from tOPV to bOPV, regarding assessment of vaccination status and vaccination of children who might have received poliovirus vaccine outside the United States, to ensure that children living in the United States (including immigrants and refugees) are protected against all three poliovirus types. This guidance is not new policy and does not change the recommendations of ACIP for poliovirus vaccination in the United States. Children living in the United States who might have received poliovirus vaccination outside the United States should meet ACIP recommendations for poliovirus vaccination, which require protection against all three poliovirus types by age-appropriate vaccination with IPV or tOPV. In the absence of vaccination records indicating receipt of these vaccines, only vaccination or revaccination in accordance with the age-appropriate U.S. IPV schedule is recommended. Serology to assess immunity for children with no or questionable documentation of poliovirus vaccination will no longer be an available option and therefore is no longer recommended, because of increasingly limited availability of antibody testing against type 2 poliovirus.

Preventing Polio Post-eradication: Revertant Proportion Patterns of OPV Serotypes

Background As wild poliovirus is eradicated and countries switch from oral polio vaccine (OPV) to inactivated polio vaccine (IPV), preventing circulating vaccine-derived poliovirus is a top priority. However, the stability of Sabin vaccine serotypes remains a concern in undervaccinated communities. We sought to measure the canonical point mutation rates associated with OPV serotype neuroreversion and vaccine-associated paralytic polio (VAPP) as possible markers of serotype fitness. Mexico provides a natural environment to study these patterns as it provides routine IPV immunization and bi-annual OPV campaigns.Methods We enrolled 450 households with children eligible for OPV before the February 2015 national immunization week from three communities near Orizaba, Mexico. In each community, a different proportion of eligible children received OPV (10, 30, and 70%). Transmission was measured by PCR detection of OPV in samples collected serially from vaccinated children, their households, and other families in the community. Positive samples were reanalyzed to quantify revertant proportion (RP), the percent of OPV VAPP mutants found in positive samples.Results15,109 samples were collected and analyzed from 1,828 participants. 554 (3.7%) were OPV positive, and 194 have been reanalyzed for RP to date.The majority of OPV 1 positive samples showed <25% revertance as late as 71 days post-vaccination (Figure 1). By contrast, OPV 2 and OPV 3 positive samples quickly revert to VAPP OPV. The majority of OPV 2 positive samples were >75% revertant by Day 7 (Figure 2), while the majority of OPV 3 positive samples were >75% revertant by Day 4 (Figure 3).Conclusion OPV 1 appears to be more stable than OPV 2 and OPV 3, remaining <25% revertant 71 days post-vaccination. OPV 2 reverts quickly, with most samples reverting to VAPP by Day 7, while OPV 3 reverts the fastest, with most samples reverting to VAPP by Day 4. Understanding the stability of OPV and VAPP mutants may shed some light on the ability of OPV serotypes to persist in community circulation. Analyses regarding potential covariates for VAPP and RP are currently underway.Figure 1:OPV 1 RP over time.Figure 2:OPV 2 RP over time.Figure 3:OPV 3 RP over time.Disclosures All authors: No reported disclosures.

World Health Organization in the African Region: Picking the Gauntlet in the Fight against Poliomyelitis in the African Region

This paper reviews the status of polio eradication in the African Region. The fight against the scourge of poliomyelitis in the African Region continues with greater focus and determination on the part of the WHO African Region, its partners and governments despite the report of new cases at the point the Region was set to celebrate victory. The discovery of four new cases in July 2016 in previously insecure areas of Borno State, Nigeria, 24 months after the last case, increased the zeal to press on. By June 2017, almost 10 months passed since the latest case of wild polio virus reported in Nigeria on 21 August 2016; and 8 months since the latest circulating vaccine derived poliovirus type 2 (cVDPV2) in Nigeria. The search for polioviruses in humans (acute flaccid paralysis surveillance) and in environmental samples is being intensified. The Region has also remained on track with the different objectives of the global Polio Eradication and Endgame Strategic Plan 2013-2018. All 47 countries switched from trivalent Oral Polio Vaccine (tOPV) to bivalent Oral Polio Vaccine (bOPV) between April 17 and May 01, 2016. Thirtyfour countries introduced inactivated polio vaccine (IPV) in their routine immunization programmes. In 2016, all countries in the Region conducted phase 1 containment and documentation of polioviruses destruction in their laboratories and the African Region Commission for Certification (ARCC) of Poliovirus Eradication had accepted documentation of polio-free status from 38 out of 47 countries. The African region also documented and published best practices of polio eradication in peerreviewed journals, so that the lessons learnt from polio could benefit other public health interventions in the Region. However, governments and partners should remain committed and deploy critical resources for intensifying surveillance, prompt response to detected viruses and strengthening of immunization systems to finish the fight.

Global Stability of a SVEIR Epidemic Model: Application to Poliomyelitis Transmission Dynamics

The lack of treatment for poliomyelitis doing that only means of preventing is immunization with live oral polio vaccine (OPV) or/and inactivated polio vaccine (IPV). Poliomyelitis is a very contagious viral infection caused by poliovirus. Children are principally attacked. In this paper, we assess the impact of vaccination in the control of spread of poliomyelitis via a deterministic SVEIR (Susceptible-Vaccinated-Latent-Infectious-Removed) model of infectious disease transmission, where vaccinated individuals are also susceptible, although to a lesser degree. Using Lyapunov-Lasalle methods, we prove the global asymptotic stability of the unique endemic equilibrium whenever . Numerical simulations, using poliomyelitis data from Cameroon, are conducted to approve analytic results and to show the importance of vaccinate coverage in the control of disease spread.

A new challenge for the world: the eradication of polio.

Poliovirus infects 100% of susceptible individuals and causes acute flaccid paralysis in one out of200 infections. Type 1 causes epidemic poliomyelitis; type 2 has been eradicated worldwide; and type 3 is close to being eradicated. In this region, the last case of wild poliovirus occurred in Peru in 1991. There are still two endemic countries: Afghanistan and Pakistan, but countries where there is no circulation of the wild poliovirus have also reported imported cases of polio. In May 2012, the World Health Assembly declared the polio eradication a programmatic emergency for global public health and, as a result, developed the Polio Eradication and Endgame Strategic Plan 2013-2018. The Plan has four objectives: 1) Detect and interrupt all poliovirus transmission and maintain surveillance of acute flaccid paralysis in children < 15 years. 2) Strengthen immunization systems and withdraw oral polio vaccine by the first trimester of 2016. Replace the trivalent oral polio vaccine with the bivalent oral vaccine, containing serotypes 1 and 3, and introduce the inactivated polio vaccine in all immunization schedules to maintain immunity against poliovirus type 2. 3) Contain poliovirus and certify interruption of transmission. 4) Plan the exploitation of the fight against polio and its impact on public health. The plan is expected to reach its goals by 2018; all use of the oral polio vaccine will be interrupted thereafter. Change in immunization schedules will require pediatricians to provide advice and guidance to families depending on the varied situations of everyday practice.

Polio vaccines: WHO position paper, March 2016–recommendations

This article presents the World Health Organization’s (WHO) recommendations on the use of polio vaccine excerpted from the WHO position paper on polio vaccines – March 2016, published in the Weekly Epidemiological Record [1]. This position paper on polio vaccines replaces the 2014 WHO position paper [2]. The position paper summarizes the WHO position on the introduction of at least one dose of inactivated polio vaccine (IPV) into routine immunization schedules as a strategy to mitigate the potential risk of re-emergence of type 2 polio following the withdrawal of Sabin type 2 strains from oral polio vaccine (OPV) [3].Footnotes to this paper provide a number of core references including references to grading tables that assess the quality of the scientific evidence, and to the evidence-to-recommendation table. In accordance with its mandate to provide guidance to Member States on health policy matters, WHO issues a series of regularly updated position papers on vaccines and combinations of vaccines against diseases that have an international public health impact. These papers are concerned primarily with the use of vaccines in large-scale immunization programmes; they summarize essential background information on diseases and vaccines, and conclude with WHO’s current position on the use of vaccines in the global context. This position paper reflects the global switch from trivalent to bivalent OPV which took place in April 2016. Recommendations on the use of polio vaccines have been discussed on multiple occasions by SAGE, most recently in October 2016; evidence presented at these meetings can be accessed at: http://www.who.int/immunization/sage/previous/en/index.html.

Wild and vaccine-derived poliovirus circulation, and implications for polio eradication.

Polio cases due to wild virus are reported by only three countries in the world. Poliovirus type 2 has been globally eradicated and the last detection of poliovirus type 3 dates to November 2012. Poliovirus type 1 remains the only circulating wild strain; between January and September 2016 it caused 26 cases (nine in Afghanistan, 14 in Pakistan, three in Nigeria). The use of oral polio vaccine (OPV) has been the key to success in the eradication effort. However, paradoxically, moving towards global polio eradication, the burden caused by vaccine-derived polioviruses (VDPVs) becomes increasingly important. In this paper circulation of both wild virus and VDPVs is reviewed and implications for the polio eradication endgame are discussed. Between April and May 2016 OPV2 cessation has been implemented globally, in a coordinated switch from trivalent OPV to bivalent OPV. In order to decrease the risk for cVDPV2 re-emergence inactivated polio vaccine (IPV) has been introduced in the routine vaccine schedule of all countries. The likelihood of re-emergence of cVDPVs should markedly decrease with time after OPV cessation, but silent circulation of polioviruses cannot be ruled out even a long time after cessation. For this reason, immunity levels against polioviruses should be kept as high as possible in the population by the use of IPV, and both clinical and environmental surveillance should be maintained at a high level.

OUR PROGRESS AGAINST POLIO - ERADICATION STILL REMAINS CHALLENGE

Polioviruses are enteroviruses that are transmitted direct from person to person or following excretion in feces or pharyngeal secretions. Because the poliovirus receptor is only expressed on human cells or on cells of few subhuman primate species, eradication is possible. In 1988 the Global Initiative for Polio Eradication (GIPE) at the 41st WHO summit announced that the main goal for 2000 is complete polio eradication. According the CDC reports the aim has not been reached yet, although the incidence of polio cases were decreased from 350,000 cases of wild polio virus in more than 125 endemic countries in 1988 to only 400 cases of polio reported in only 3 endemic countries (Nigeria, Afghanistan and Pakistan) in 2000. The last case of wild polio virus (wPV) was detected in 1997 in Serbia. In order to eradicate polio virus two vaccines are used- inactivated and live-attenuated polio vaccines. According to the studies oral polio vaccine has better efficacy and immunogenicity profile in comparison to inactivated polio vaccines, but due to safety reasons inactivated polio vaccine is now widely used (there is no risk of vaccine associated paralytic polio - VAPP and vaccine derived polio virus- VDPV). Although there are very effective and immunogenic vaccines available all over the world the polio eradication is not a simple project, in undeveloped and developing countries vaccines are not available, whereas in developed countries parents refused to vaccinate their children.

Preventing Polio Post-Eradication: Elucidating Polio Virus Shedding and Transmission Patterns in the Presence of Inactivated Polio Vaccine and Oral Polio Vaccine

Preventing Polio Post-Eradication: Elucidating Polio Virus Shedding and Transmission Patterns in the Presence of Inactivated Polio Vaccine and Oral Polio Vaccine

Sex-differential effects on mortality of BCG and diphtheria-tetanus-pertussis vaccines in a rural area with high vaccination coverage: observational study from Senegal

Diphtheria-tetanus-pertussis (DTP) may be associated with increased female mortality; the effect of co-administration with BCG is not known. Between 1989 and 1997, we examined female and male mortality rates in rural Senegal where 7824 infants received the first dose of DTP and inactivated polio vaccine (DTP-IPV) with BCG. Subsequent doses of DTP-IPV were administered alone. We analysed mortality according to sex and number of doses of DTP-IPV vaccine. BCG and DTP-IPV1 simultaneously reduced mortality from 60/1000 person-years in unvaccinated girls to 35/1000 person-years, but mortality increased with subsequent doses of DTP-IPV to 45/1000 person-years. Among boys, BCG and DTP-IPV1 simultaneously reduced mortality from 72/1000 person-years to 60/1000 person-years and mortality decreased further with subsequent doses of DTP-IPV to 34/1000 person-years. In age-adjusted analyses, female-male mortality rate ratios were 0.83(95% CI 0.50-1.40) among unvaccinated children and 0.58 (95% CI 0.35-0.96) among children vaccinated simultaneously with BCG and DTP-IPV1, but increased to 1.17 (95% CI 0.67-2.03) after DTP-IPV2, and 1.63 (95% CI 0.86-3.10) after DTP-IPV3. Difference in vaccination coverage could not explain these sex-differential patterns; girls had significantly better weight-for-age than boys so nutritional status did not explain the increase in female mortality after DTP-IPV3. Whereas BCG co-administered with DTP-IPV was associated with lower female than male mortality, subsequent DTP-IPV vaccinations were associated with an increase in female mortality relative to male mortality.

Acceptance of multiple injectable vaccines in a single immunization visit in The Gambia pre and post introduction of inactivated polio vaccine

BackgroundAs the World Health Organization (WHO) currently recommends that children be protected against 11 different pathogens, it is becoming increasingly necessary to administer multiple injectable vaccines during a single immunization visit. In this study we assess Gambian healthcare providers’ and infant caregivers’ attitudes and practices related to the administration of multiple injectable vaccines to a child at a single immunization visit before and after the 2015 introduction of inactivated polio vaccine (IPV). IPV introduction increased the number of injectable vaccines recommended for the 4-month immunization visit from two to three in The Gambia. MethodsWe conducted a cross-sectional questionnaire-based survey before and after the introduction of IPV at 4months of age in a representative sample of all health facilities providing immunizations in The Gambia. Healthcare providers who administer vaccines at the selected health facilities and caregivers who brought infants for their 4month immunization visit were surveyed. FindingsPrior to IPV introduction, 9.9% of healthcare providers and 35.7% of infant caregivers expressed concern about a child receiving more than 2 injections in a single visit. Nevertheless, 98.8% and 90.9% of infants received all required vaccinations for the visit before and after IPV introduction, respectively. The only reason why vaccines were not received was vaccine stock-outs. Infant caregivers generally agreed that vaccinators could be trusted to provide accurate information regarding the number of vaccines that a child needed. ConclusionHealthcare providers and infant caregivers in this resource limited setting accepted an increase in the number of injectable vaccines administered at a single visit even though some expressed concerns about the increase.

Factors determining anti-poliovirus type 3 antibodies among orally immunised Indian infants

BackgroundAmong the three poliovirus serotypes, the lowest responses after vaccination with trivalent oral polio vaccine (tOPV) are to serotype 3. Although improvements in routine immunisation and supplementary immunisation activities have greatly increased vaccine coverage, there are limited data on antibody prevalence in Indian infants. MethodsChildren aged 5–11months with a history of not having received inactivated polio vaccine were screened for serum antibodies to poliovirus serotype 3 (PV3) by a micro-neutralisation assay according to a modified World Health Organization (WHO) protocol. Limited demographic information was collected to assess risk-factors for a lack of protective antibodies. Student’s t-test, logistic regression and multilevel logistic regression (MLR) model were used to estimate model parameters. ResultsOf 8454 children screened at a mean age of 8.3 (standard deviation [SD]-1.8) months, 88.1% (95% confidence interval (CI): 87.4–88.8) had protective antibodies to PV3. The number of tOPV doses received was the main determinant of seroprevalence; the maximum likelihood estimate yields a 37.7% (95% CI: 36.2–38.3) increase in seroprevalence per dose of tOPV. In multivariable logistic regression analysis increasing age, male sex, and urban residence were also independently associated with seropositivity (Odds Ratios (OR): 1.17 (95% CI: 1.12–1.23) per month of age, 1.27 (1.11–1.46) and 1.24 (1.05–1.45) respectively). ConclusionSeroprevalence of antibodies to PV3 is associated with age, gender and place of residence, in addition to the number of tOPV doses received. Ensuring high coverage and monitoring of response are essential as long as oral vaccines are used in polio eradication.