Booster vaccination of adults with measles-mumps-rubella may provide partial protection against COVID-19 disease

Aims: The study aimed to investigate COVID-19 seropositivity rate in vaccinated and non-vaccinated adult groups to see if booster live attenuated vaccinations have a protective effect against COVID-19 in an isolated cluster of adults. Methods: Our retrospective cohort study was conducted on 257 participants who were tested for COVID-19 PCR and shared the same accommodation and the same dining hall. Participants were divided according to their vaccination status into two groups. The rate of COVID-19 seropositivity, age, body mass index (BMI), active smoking, presence of comorbidity was compared between these two groups. Results: 245 of 257 people accepted to participate in the study and 36.7% (n = 90) were COVID 19 positive. All of the participants were healthy, male, young adults. The non-vaccinated cases (n=207) had higher rates of COVID-19 seropositivity than the vaccinated cases (n=38) (40.6% vs 15.8%)(Odds ratio [95%Cl]=3.6 [1.5-9.0], p=0.004), while who were similar in terms of age, comorbidities rates, active smoking status and BMI (p=0.305, p=0.594, p=0.280 and p=0.922, respectively). Conclusion: Based on these results, we cautiously predict that immunity produced by MMR vaccination boosters may make adults less susceptible to COVID-19. Keywords: COVID-19; live attenuated vaccines; booster vaccination; MMR.