![]() ![]() We found that most of the individuals had neutralizing antibodies to the Delta variant at the time of receiving their first dose of BBV152 vaccine. In this work, we enrolled adult subjects from the general population who got vaccinated with BBV152 as part of a routine COVID-19 vaccination program and assessed the effect of pre-existing antibody levels on boosting of antibody titers after receiving a single dose of vaccine. As antibody levels wane and the risk of reinfection with the same variant and or a new variant warrants booster vaccination, it is imperative to understand the efficiency of boosting vis-à-vis pre-existing antibody levels. We aimed to measure the impact of pre-existing humoral immunity on response to subsequent vaccination with one dose of BBV152. A larger proportion of people in India got vaccinated after the second wave in 2021. Anti-spike antibodies measured by ELISA were about five-fold higher after one dose of CoronaVac in participants with prior COVID-19 infection and no further increase in antibodies was observed after the second dose of the vaccine 8.īBV152 was one of the two vaccines licensed in India and now in over 20 other countries. In a cohort of healthcare workers in Brazil, about 48% of participants of the study had prior history of SARS-CoV-2 infection at the time of receiving the first dose of CoronaVac, an inactivated whole SARS-CoV-2 vaccine 8. These antibodies were capable of neutralizing different variants of concern of SARS-CoV-2 7. Similarly, previously-infected individuals receiving a single dose of ChAdOx1 nCoV-19 generated neutralizing antibodies equivalent to that generated after two doses of BNT162b2 vaccine in naive individuals. The group which received the first dose of mRNA vaccine more than 3 months after SARS-CoV-2 infection generated higher levels of neutralizing antibodies compared to the other two groups 6. Another study has shown that the neutralizing antibody titers varied in the three groups of individuals who were vaccinated with BNT162b2 mRNA vaccine either 1 to 2 months, 2 to 3 months, or more than 3 months after infection. In the case of mRNA vaccines, antibody response in individuals with prior history of natural SARS-CoV-2 infection was at least one order of magnitude higher compared to seronegative individuals 4, 5. There are a number of reports assessing the effect of prior infection on antibody responses post-vaccination. A subsequent serosurvey from Delhi showed seropositivity of over 90% 3 suggesting that India was/is a heterogeneous mix of people with immunity to COVID-19 due to vaccination or natural infection or both after the second wave of SARS-CoV-2 cases. Serosurveillance studies have shown that 69% of the Indian population had antibodies for COVID-19 after the second wave of SARS-CoV-2 infections between April 2021 and June 2021 2. Less than 10% of the Indian population had received one dose of COVID-19 vaccine at the onset of second wave of COVID-19 in April 2021. These two vaccines have been the mainstay of COVID-19 vaccination program in India. In India, the viral-vectored ChAdOx1 nCoV-19 and the inactivated BBV152 vaccines were approved for use in adults in 20. Inactivated vaccines have catered to almost half of the world’s COVID-19 vaccine needs 1.
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