97% Tamil Nadu elderly population has protective immunity; what's seropositivity
What's the story
A recent serosurvey in Tamil Nadu has found that 97% of the elderly population in six districts have protective immunity against COVID-19. The survey, conducted by the Directorate of Public Health and Preventive Medicine (DPH) in April, tested blood samples from 3,643 individuals across Chennai, Tiruvallur, Tiruvannamalai, Tiruchi, Dharmapuri, and Kanniyakumari. This is the fifth phase of the survey and comes three and a half years after the last one was conducted in December 2021.
Survey details
High seroprevalence of protective antibodies
The DPH said that preliminary analysis of 1,214 samples showed 97% of the surveyed population had protective levels of SARS-CoV-2 IgG antibodies. The DPH noted that despite a three-and-a-half-year gap since the last survey, the current phase recorded a very high and significant prevalence of protective antibodies. It added that effective vaccination drives by the state government may have contributed to this high level of immunity.
Immunity enhancement
Natural infections may have further enhanced antibody development
The DPH also suggested that natural infections and subclinical infections due to the weakened circulating Omicron sub-lineage of the virus may have further enhanced antibody development. It noted that due to the high seroprevalence of antibodies, SARS-CoV-2 could not cause severe illness in Tamil Nadu, where COVID-19 deaths are almost nil. The state has not officially released detailed data on COVID-19 cases following the recent surge across India.
Significance
Significance of seropositivity
A seropositive test result often indicates that a person has been exposed to or infected with a virus or other infectious agent and has developed antibodies against it. It helps health authorities understand how widely a disease has spread in a community. Tamil Nadu's 97% seropositivity among the elderly is reassuring, especially since global studies show varying effectiveness of vaccines in creating antibodies. A 2023 analysis noted around 67% seropositivity after three doses of COVID-19 vaccines.
Public health advice
Vulnerable groups should take precautions: Minister
Tamil Nadu Health Minister Ma Subramanian said that while the survey indicates increased immunity levels in the state, vulnerable groups such as those with co-morbidities, pregnant women, immunocompromised individuals, and the elderly should take precautions in public places. The DPH had sent 19 samples from Tamil Nadu to the Institute of Virology in Pune for testing, which only found non-virulent Omicron variants.