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Chennai, June 12, 2025 – A recent serosurvey conducted by Tamil Nadu’s Directorate of Public Health has revealed that at least 97% of senior citizens in the state have developed immunity against Covid-19. The survey, carried out in April 2025, targeted elderly populations across districts such as Chennai, Tiruvallur, Tiruvannamalai, Trichy, Dharmapuri, and Kanyakumari.
Preliminary analysis of 1,214 samples from this group showed a protective immunity rate of 97%. The survey is part of a broader effort that has tested more than 25,000 samples per phase, using population-proportionate sampling techniques to ensure uniform data collection across the state.
Health Minister Ma Subramaniam highlighted the significant progress made since the early days of the pandemic. “We saw a boost in immunity since 2020. The first phase in October 2020 showed 32% immunity, which rose to 29% in April 2021 and 70% in August 2021. By December 2021, immunity had reached 87%,” he stated.
Officials attributed the high immunity rates to a combination of effective vaccination campaigns and natural infections. “We vaccinated more than 95% of the population with at least one dose of the vaccine. Besides this, natural infections due to the circulation of weakened mutations such as Omicron sub-lineages of the virus have further enhanced antibody development, contributing to hybrid immunity,” explained Dr. T S Selvavinayagam, Director of Public Health.
High seroprevalence, as seen in the survey, indicates that most individuals in the sample have antibodies in their blood, signifying exposure to the virus through infection or vaccination. This is generally associated with some level of protection against future infections. The officials noted that the virus has largely been unable to cause severe illness or death among those infected in recent times.
Disclaimer:
The information in this news article is based on preliminary findings from a serosurvey conducted by the Tamil Nadu Directorate of Public Health. While high seroprevalence suggests widespread immunity, it does not guarantee complete protection against Covid-19 for every individual. The results may not be representative of all demographic groups and should be interpreted as part of ongoing public health monitoring. Readers are advised to continue following official health guidelines and consult healthcare professionals for personalized advice.
