KOCHI: COVID-19 cases have been spiking steadily in Kerala, with total confirmed cases already breaching the one-lakh mark and active cases crossing 32,000. The world is keenly focused on developing a vaccine which could bring an end to the pandemic, but herd immunity looks to be the solution to restore normal life in the present situation. Herd immunity is the stage where a majority of people in a society develop immunity, either through vaccination or because they were infected earlier, thereby saving the rest of the members from contracting the virus.
Studies say that at least 50% of the population should be immune in order to achieve herd immunity. Population immunity is estimated through cross-sectional surveys of representative samples using serological tests. Surveys conducted in countries such as Italy and Spain, where the infection rate was high during early days of the pandemic, suggest that nationwide prevalence of antibodies varies between 1% and 10%, with a peak of around 10%-15% in heavily affected urban areas.
“With flu pandemics, herd immunity is usually attained after two to three epidemic waves. In the case of Covid-19, which has an estimated infection fatality rate of 0.3-1.3%, the cost of reaching herd immunity through natural infection would be very high, especially in the absence of improved patient management and without optimal shielding of individuals at risk of severe complications,” said a public health expert. “The road to achieve herd immunity is tough as one can’t predict the turn of events in the coming months. The cases are likely to peak, but the chances of reinfection and also the second wave of Covid cases hitting globally should be considered in this scenario,” he added.
In the case of Kerala, which has a population of around 3.48 crore, 1.5 crore should be either vaccinated or suffer infection to achieve herd immunity. “So, some districts where too many people are getting infected might reach that 50%-mark early,” said Monu Varghese, a pulmonologist.Meanwhile, Dr Rojo Joy, Kochi-based neonatologist, said that an effective vaccine presents the safest way to reach herd immunity. “Though it’s a long road, it’s the only way ahead to get rid of the virus. It might take a year more to achieve this. Vaccines are particularly suited for creating herd immunity because their allocation can be specifically targeted to highly exposed populations,” said Dr Rojo.