Kerala seems to be an outlier with a. to be daily infection rate of more than 20,000 even if all other states report fewer figures. The weekly average of new Covid-19 cases in the state has skyrocketed and the reproductive value, an indication of how contagious the virus will be, is well above the national average.
What explains the situation in Kerala? Bhramar Mukherjee, a biostatistician at the University of Michigan, argues that this could be due to higher tests and a low seroprevalence value. In a tweet she wrote: “Kerala runs almost three times more tests than West Bengal (which has a three times larger population), has a seroprevalence of around 43% (68% nationally), CFR 0.5% (1.3% nationally) . “
In other words, a low seroprevalence score means the majority of the state’s population has not yet developed antibodies. You are therefore prone to infection, and higher tests are a way to detect this. While the state continues to report much higher numbers of daily cases, the death rate is much lower than the national average.
Gautam Menon, a professor at Ashoka University, told India Today, “These results are broadly in line with expectations. I note that Kerala, a state that has not hesitated to enforce strict distancing enforcement measures, has a relatively low seroprevalence compared to any other state. “
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Compare this with the situation in Madhya Pradesh and Rajasthan, the two states with very high seroprevalence values. While the seroprevalence value in Madhya Pradesh is 79 percent, it is 76.2 percent in Rajasthan.
Seroprevalence tells us about the percentage of the population with antibodies to fight infection, according to the Centers for Disease Control and Prevention. A higher seroprevalence means that more people have encountered Covid-19 and developed antibodies to the virus.
According to a survey by the Indian Council of Medical Research, Assam and Kerala are the two states with the lowest seroprevalence. They are the ones who have reported a higher number of cases in the past few weeks.
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The data also shows that states with lower seroprevalence test more. While Kerala has 753 tests per 1,000 residents against the national average of 339, the numbers for Madhya Pradesh and Rajasthan are 168 and 162, respectively.
Although the high seroprevalence in many states except Kerala, Assam and Maharashtra indicates the presence of antibodies in a large segment of the population, vigilance towards the virus cannot be reduced.
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“The fourth national sero-survey contains useful information, but again it should not give us any certainty about herd immunity,” said Bhramar Mukherjee in another tweet. There are large regional differences and with more transmissible variants, the herd immunity threshold is raised to 80 to 85 percent, she argues.
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