The Impact of Vaccine Activated Immunity Enhancement on SARS-CoV-2 Spread Dynamics in India and IgG Antibodies Prevalence in Japan Population

We reported the percentage of SARS-CoV-2 IgG antibodies generated in the Indian population from natural infection and vaccination. The waning of the antibodies over time has also been worked out. The article discusses the overall findings in India, the states (Tamil Nadu, Haryana, and Odisha), and Delhi. The abstract covers the Tamil Nadu’s data pattern only, the main part of the paper has similar data from other states (Haryana and Odisha), the city of Delhi, and overall, India. Seroprevalence in Tamil Nadu increased to 87% in the fourth survey conducted in December 2021 from 70% in the third survey undertaken in July 2021. As of April 2021, 29% of residents were seropositive, but by July–August 2021, there was a steep rise to 70% in the third survey. By August 1, 2021, 22% and 6.2% of the state’s total population had received single- and two-dose vaccinations respectively. The third serosurvey, which spanned until August, suggested that vaccination might have contributed to the seroprevalence in Tamil Nadu. Considering the third and fourth surveys’ full vaccination figures of the state, 22.1% antibody enhancement had to have happened. However, only a 17% increase was reported, a decline of 5.1%. Whereas, considering the eligible population, the percentage reduction in seroprevalence (waning of antibodies) was higher at 11.7% that occurred in 4–5 months. In August 2020, the monthly caseload of Tamil Nadu reached a plateau of 182,182 during the original Wuhan (first) wave. When the first wave receded, baseline cases were the lowest at 21,263 in January 2021. Cases peaked at 929,760 in May 2021 and fell to 21,128 in December 2021, during the second Delta wave that hit Tamil Nadu. In January 2022, the Omicron surge (third wave) reached a plateau with 597,175 cases. Cases decreased in February 2022, with the lowest monthly caseloads recorded in April and May at 1542 and 1107, respectively. Seropositivity of 32.0% measured in the first survey (October and November 2020) and 29% seroprevalence reported in the second survey (April 2021) were due to the first original Wuhan wave that hit the state and peaked in August 2020. As a result of the strong Delta wave, which peaked in May 2021, and vaccination (22% partial, 6.2% full) done in the state, the seroprevalence increased to 70% in the third survey (July–August 2021). A monthly caseload of 597,175 cases in January 2022 (Omicron wave) led to an 87% seropositivity rate (fourth survey), which also includes vaccine-generated immunity as 28.3% of the total population and 36.8% of those who were eligible vaccinated to contribute to the survey done in Tamil Nadu. A small section of the paper examines the seroprevalence (%) in the Japanese population. We covered Okinawa’s main and remote islands and the city of Kobe.