Assessment of poliovirus antibody seroprevalence in polio high risk areas of West Africa

Nutritional Status Link with Polioseronegativity Among Children from Poliomyelitis Transmission High-Risk Area of the Democratic Republic of the Congo (DRC)

Background

Malnutrition is identified as a risk-factor for insufficient polioseroconversion in the context of a vaccine-derived polio virus (VDPV) outbreak prone region. To assess the prevalence of malnutrition and its link to poliovirus insufficient immunity, a cross-sectional household survey was conducted in the regions of Haut- Lomami and Tanganyika, DRC.

Methods

In March 2018, we included 968 healthy children aged 6 to 59 months from eight out of 27 districts. Selection of study locations within these districts was done using a stratified random sampling method, where villages were chosen based on habitat characteristics identified from satellite images. Consent was obtained verbally in the preferred language of the participant (French or Swahili) by interviewers who received specific training for this task. Furthermore, participants contributed a dried blood spot sample, collected via finger prick. To assess malnutrition, we measured height and weight, applying WHO criteria to determine rates of underweight, wasting, and stunting. The assessment of immunity to poliovirus types 1, 2, and 3 through the detection of neutralizing antibodies was carried out at the CDC in Atlanta, USA.

Results

Of the study population, we found 24.7% underweight, 54.8% stunted, and 15.4% wasted. With IC95%, underweight (OR=1.50; [1.11-2.03]), and the non-administration of vitamin A (OR=1.96; [1.52-2.54]) were significantly associated with seronegativity to polioserotype 1. Underweight (OR=1.64; [1.20-2.24]) and the non-administration of vitamin A (OR=1.55; [1.20-2.01]) were significantly associated with seronegativity to polioserotype 2. Underweight (OR=1.50; [1.11-2.03]), and the non-administration of vitamin A (OR=1.80. [1.38-2.35]) were significantly associated with seronegativity to polioserotype 3. Underweight (OR=1.68; IC95% [1.10-2.57]) and the non-administration of vitamin A (OR=1.82; IC95% [1.30-2.55]) were significantly associated with seronegativity to all polioserotypes.

Conclusion

This study reveals a significant association between underweight and polioseronegativity in children. In order to reduce vaccine failures in high-risk areas, an integrated approach by vaccination and nutrition programs should be adopted.

Prediction Model with Validation for Polioseronegativity in Malnourished Children from Poliomyelitis Transmission High-Risk Area of the Democratic Republic of the Congo (DRC)

Background

Malnutrition is identified as a risk factor for insufficient polio seroconversion in the context of a vaccine-derived poliovirus (VDPV) outbreak-prone region. In the Democratic Republic of Congo (DRC), underweight decreased from 31% (in 2001) to 26% (in 2018). Since 2004, VDPV serotype 2 outbreaks (cVDPV2) have been documented and were geographically limited around the Haut-Lomami and Tanganyika Provinces.

Methods

To develop and validate a predictive model for poliomyelitis vaccine response in malnourished infants, a cross-sectional household study was carried out in the Haut-Lomami and Tanganyika provinces. Healthy children aged 6 to 59 months (n=968) were enrolled from eight health zones (HZ) out of 27, in March 2018. We performed a bivariate and multivariate logistics analysis. Final models were selected using a stepwise Wald method, and variables were selected based on the criterion p < 0.05. The association between nutritional variables, explaining polio seronegativity for the three serotypes, was assessed using the receiver operating characteristic curve (ROC curve).

Results

Factors significantly associated with seronegativity to the three polio serotypes were underweight, non-administration of vitamin A, and the age group of 12 to 59 months. The sensitivity was 10.5%, and its specificity was 96.4% while the positive predictive values (PPV) and negative (PNV) were 62.7% and 65.3%, respectively. We found a convergence of the curves of the initial sample and two split samples. Based on the comparison of the overlapping confidence intervals of the ROC curve, we concluded that our prediction model is valid.

Conclusion

This study proposed the first tool which variables are easy to collect by any health worker in charge of vaccination or in charge of nutrition. It will bring on top, the collaboration between the Immunization and the Nutritional programs in DRC integration policy, and its replicability in other low- and middle-income countries with endemic poliovirus.

Suboptimal Serologic Immunity Against Poliomyelitis Among New Migrant Children in Greece Calls for Organized Action

BACKGROUND

Migration-flows pose the risk of poliovirus reintroduction from endemic countries to Greece. This study aims to evaluate serologic-immunity/vaccination against poliomyelitis in newly-arriving migrant children.

METHODS

Demographic-immunisation data and blood-serum were obtained from migrants 1-14years-old, referred to a hospital-clinic in Athens-Greece within three months from arrival. Immunity to polioviruses-1-3 was determined by serum-neutralizing-antibodies(WHO guidelines). Titers ≥ 1:8 were considered positive.

RESULTS

From 9/2010 to 9/2013, 274 children(150 refugees/124 immigrants), mean age 7.1years-old, were enrolled. Only 57(20.8%) of them presented with vaccination-records. Children originated mainly from Asia(n = 198), Eastern Europe(n = 28), Middle East(n = 24) and Africa(n = 24) with 160(58.4%) from polio-endemic-countries(Afghanistan-112(40.8%), Pakistan-24(8.8%) and India-24(8.8%)). Seropositivity against polio-1-2&3 was 84.3%, 86.1% and 74.5%, respectively. Immigrants, had higher seroprotective rates against polioviruses-1-2&3 than refugees(polio-1:p = 0.002;polio-2:p = 0.004,polio-3:p < 0.001). Seronegativity to 1PVs-2PVs and all three polio serotypes was found in 37(13.5%),12 (4.4%), and 30 children(10.9%) respectively. Increasing number of vaccine-doses, and younger-age, were positively-associated with seropositivity.

DISCUSSION

A remarkable fraction of newly-arrived migrant-children were seronegative to one or more polioviruses.

Poliovirus Immunity among Children Aged 6-11 and 36-48 Months in 14 Polio High-Risk Provinces of Afghanistan: A Health-Facility-Based Study

Afghanistan is one of two countries where wild poliovirus (WPV) type 1 remains endemic. We conducted a facility-based cross-sectional survey of antipoliovirus antibodies in children in 14 provinces of Afghanistan. The provinces were selected based on programmatic priorities for polio eradication. Children aged 6–11 and 36–48 months attending outpatient clinics were enrolled in the study. We collected venous blood, isolated serum, and conducted neutralization assays to detect poliovirus neutralizing antibodies. A total of 2086 children from the 14 provinces were enrolled. Among the enrolled children, 44.3% were girls; the median age in the 6–11-month group was 9.4 months, and in the 36–48-month group, it was 41.8 months. The most common spoken language was Pashtu (70.8%). Eighty-two percent of children were fully immunized against all the diseases in the vaccination schedule of Afghanistan. In the children aged 6–11 months, seroprevalence to poliovirus type 1 (PV1) was 96.5% and seroprevalence to poliovirus type 3 (PV3) was 93%; in children aged 36–48 months, seroprevalence to PV1 was 99.5% and to PV3 was 98%. Antipoliovirus antibody prevalence for poliovirus type 2 (PV2) was 70.5% in the younger group compared with 90.9% in the older children. Children from Herat and Laghman provinces had almost 100% seroprevalence to PV1, and other provinces also had high prevalence, ranging from 92.0% to 99.0%. A similar finding was seen for antibodies against PV3, ranging from 88% to 100% by province. On the contrary, antibodies to PV2 were low, ranging from 53% for children in the Khost province to around 89% in Kunduz. There was a cluster of 18 seronegative children in the Nuristan province. Overall, the polio eradication program of Afghanistan has been successful in achieving high seroprevalence of poliovirus neutralizing antibodies in the parts of the country included in this study.

Implication of a High Risk for Type 2 Vaccine-Derived Poliovirus Emergence and Transmission After the Switch From Trivalent to Bivalent Oral Poliovirus Vaccine

BACKGROUND

China implemented the globally synchronized switch from trivalent oral poliovirus vaccine (tOPV) to bivalent OPV (bOPV) and introduced 1 dose of inactivated poliovirus vaccine on 1 May 2016. We assessed the impact of the switch on the immunity level against poliovirus, especially type 2.

METHODS

Children born between 2014 and 2017, who were brought to the hospitals in Urumqi city, Xinjiang Province in 2017, were enrolled and blood samples were collected to test for antibody titers against poliovirus. A comparison of seroprevalence between the children born before (preswitch group) and after the switch (postswitch group) was performed to assess the impact of the switch on the immunity level against polio.

RESULTS

A total of 172 subjects were enrolled. The overall seroprevalences were 98.8%, 79.1%, and 98.3% for types 1, 2, and 3, respectively. Seroprevalence for type 2 significantly decreased from 91.6% in the preswitch group to 67.4% in the postswitch group, but no statistically significant change was observed for both types 1 and 3.

CONCLUSIONS

The switch from tOPV to bOPV can provide high-level immunity against types 1 and 3 but not against type 2, indicating a high risk of type 2 vaccine-derived poliovirus emergence and transmission.

Achieving High Poliovirus Antibody Seroprevalence in Areas at Risk of Vaccine-Derived Poliovirus Transmission-Niger Experience

Background

Outbreaks of vaccine-derived poliovirus type 2 (VDPV2) continue to expand across Africa. We conducted a serological survey of polio antibodies in high–polio risk areas of Niger to assess risk of poliovirus outbreaks.

Methods

Children between 1 and 5 years of age were enrolled from structures randomly selected using satellite imaging enumeration in Diffa Province, Niger, in July 2019. After obtaining informed consent, dried blood spot cards were collected. Neutralizing antibodies against 3 poliovirus serotypes were detected using microneutralization assay at the Centers for Disease Control and Prevention.

Results

We obtained analyzable data from 309/322 (95.9%) enrolled children. Seroprevalence of polio antibodies was 290/309 (93.9%), 272/309 (88.0%), and 254/309 (82.2%) for serotypes 1, 2, and 3, respectively. For serotypes 1 and 2, the seroprevalence did not significantly change with age (P = .09 and P = .44, respectively); for serotype 3, it increased with age (from 65% in 1–2-year-olds to 91.1% in 4–5-year olds; P < .001). We did not identify any risk factors for type 2 seronegativity.

Conclusions

With type 2 seroprevalence close to 90%, the risk of emergence of new cVDPV2 outbreaks in Niger is low; however, the risk of cVDPV2 importations from neighboring countries leading to local transmission persists. Niger should maintain its outbreak response readiness capacity and further strengthen its routine immunization.