The Impact of Vaccination on the Likelihood of COVID-19 Infection.

The current study investigates COVID-19 infection likelihood using data from 5,819 respondents in Vietnam and Indonesia (December 10, 2022, to March 27, 2023) through binary logistic regressions. Descriptive statistics highlight the significance of vaccination status, with almost half of unvaccinated respondents contracting the infection. The second vaccine dose showed the lowest infection percentages, suggesting a potential dose-dependent effect. Those receiving mRNA vaccines consistently had reduced infection likelihood across the first four doses, with an unexpected reversal for the fifth dose. Vaccinated individuals, especially with mRNA vaccines, had faster recovery times, and variability in recovery times and milder symptoms were observed in mRNA vaccine recipients. Regression results from Model 1 reveal a substantial impact of vaccination, with vaccinated respondents having ∼48.1% lower odds than the unvaccinated. Model 2 underscores a dose-dependent protective effect, with each additional dose associated with a notable 6.6% reduction in infection likelihood. Beyond vaccination, gender, family size, marital status, employment, urban residence, and nationality influenced infection likelihood. Males, larger families, single marital status, unemployment, rural residence, and Indonesian nationality increased the likelihood of infection. Surprisingly, respondents with infected family members exhibited a lower infection likelihood, suggesting potential protective measures within households. These findings highlight COVID-19 dynamics, and ongoing research refines comprehension.