Immunity effect of divalent oral poliovirus vaccine on the incidence of COVID-19

In a recent study published in Immunology FrontierResearchers evaluated the effect of oral poliovirus vaccine (OPV) on the incidence of coronavirus disease 2019 (COVID-19).

Background

Rapid intervention during an emergency pandemic is important to control the transmission of the causative agent until vaccination is introduced. In the light of the COVID-19 pandemic, several measures have been taken to limit the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). These include physical distances, masking, travel restrictions, national or regional blockades, and more. While these measures are effective, they are temporary and disrupt economic and social activities. Therefore, achieving herd immunity should be the ideal solution.

In this regard, vaccines against SARS-CoV-2 were developed in record time with urgency in mind, and several vaccines were approved for emergency use. Nonetheless, many challenges have emerged regarding global expansion, especially in low-income countries where health infrastructure is underdeveloped. The emergence of variants of SARS-CoV-2 that showed substantial resistance to vaccine-induced immune responses was another obstacle.

Previous studies have suggested that live attenuated vaccines (LAVs) induce broad protection against off-targets. This was observed with OPV, measles vaccine, and Bacillus Calmette-Guerin (BCG) vaccine. According to one study, OPV reduced the incidence of influenza in the Soviet Union in the late 1960s. Therefore, it is speculated that LAV may provide a wide range of protective effects against SARS-CoV-2.

About research

In this study, researchers evaluated the effect of OPV vaccination on the incidence of COVID-19. This study was conducted at Kirov Medical College from May 14, 2020 to January 11, 2021. Participants between the ages of 18 and 65 were eligible on the condition that they were healthy without any chronic conditions or abnormalities. Excluded participants were those with a history of COVID-19 infection, immunodeficiency, immunosuppression, malignant neoplasms, vaccine hypersensitivity, or other complications.

Eligible subjects were equally randomized to study / vaccine and placebo cohorts. Participants in the study cohort received 0.2 ml of divalent OPVs 1 and 3, while placebo participants received sterile distilled water. Blood samples were obtained from 20 placebo participants and 40 vaccinated participants at each visit.

Neutralizing antibody (NAbs) for poliovirus was determined using a microneutralization assay. The main study result was to estimate the number of COVID-19 cases in each group within 3 months of OPV or placebo administration. Cases of COVID-19 were confirmed by polymerase chain reaction (PCR) or serological examination. The side effects of the study were common colds in each cohort, the total number of acute respiratory infections (ARIs) such as influenza, the severity and duration of the illness, and death.

Survey results

Overall, 558 and 557 participants were enrolled in the study and placebo cohort. The questionnaire collected data on previous ARI history and revealed that participants in each cohort often get sick twice or once a year. Participants were not vaccinated with SARS-CoV-2 before or during the study period. All participants were previously vaccinated against polio. Serum samples obtained at visits 1 and 2 showed neutralizing activity against attenuated Sabin poliovirus.

At the beginning of the study, antibodies against at least two serotypes of poliovirus were detected in all subjects. Nonetheless, eight subjects (2 from placebo and 6 from the study cohort) showed no detectable nAb titer against type 3 poliovirus, indicating weakened protection against this serotype. Suggests. At the second visit, that is, after one month of vaccine / placebo administration, placebo participants showed no increase in nAb titers.

Individuals in the study cohort, on the other hand, showed a 16-fold increase in nAb titers against type 3 poliovirus and a 5.6-fold increase over type 1 poliovirus. Approximately 25 individuals from the study cohort were diagnosed with COVID-19, compared with 44 COVID-19 cases in the placebo group, which were statistically significant. This meant that the incidence of COVID-19 was 1.8-fold lower in OPV-vaccinated subjects than in placebo recipients. No deaths have been recorded in either cohort.

Four COVID-19 cases were recorded within one month of OPV administration compared to seven placebo cohorts, but this difference was not statistically significant given the small number of cases. did. In addition, placebo recipients had a 1.9-fold higher relative risk of contracting SARS-CoV-2 than subjects who received OPV vaccination in the first month.

The ARI event was (self) reported by 68 OPV vaccinated subjects and 66 placebo recipients. Incidence of ARI was lower in vaccinated subjects than in placebo recipients. However, it was not statistically significant.

Conclusion

The findings revealed that the incidence of COVID-19 was lower among subjects vaccinated with OPV than subjects who received placebo. In addition, individuals vaccinated with OPV had a lower risk of COVID-19 infection than placebo participants.

In particular, the frequency of SARS-CoV-2 positive PCR or serological testing in contacts of people with ARI or COVID-19 was higher in the placebocohort than in vaccinated subjects. This suggests that OPV may confer resistance to SARS-CoV-2 infection. Nevertheless, more research is needed to characterize the protective effect of OPV or LAV vaccination against SARS-CoV-2.