The third round of sero surveillance conducted by the Indian Council for Medical Research (ICMR) in three districts in the State in mid-December, as part of the national sero survey, has put the sero positivity rate (IgG positivity, indicative of silent, prior exposure to SARS- CoV-2) at the time at 11.6%.
This is a jump by 14.5 times from August, when the ICMR’s second round of sero survey had indicated a sero prevalence of 0.8% in the State.
The sero survey was conducted in Ernakulam, Thrissur and Palakkad in December 2020.
The ICMR’s strategy has been to do repeated cross sectional sero studies in the same geographic locations so that the disease transmission trends can be traced. The first round of sero survey in May in the same districts had shown a sero prevalence of 0.33 %, while the second round in August showed the sero prevalence to be 0.8%.
When compared to the national average, Kerala’s sero prevalence (11.6%) as of December was just half that of the national average (21%). This shows the effectiveness of robust containment measures in the State, including quarantine, contact tracing and testing strategies, it is claimed.
However, the other side of the story is that, if the sero prevalence at the national level went up by 3.1 times between August and December, in Kerala, this went up by 14.5 times during the same period.
Extrapolating the third round sero survey results to the State’s population and comparing it with the actual number of cases that were detected in the State around that time (December), it can be seen that for every case officially diagnosed and detected, the State had missed only about six infections in the community.
Kerala fares extremely well if this is compared at the national level, wherein 30 infections were being missed for every case detected in December. This indicates the efficacy of the focussed testing strategy adopted by the State.
The sero prevalence rate thrown up by the ICMR study indicates that a huge proportion of the State’s population continues to be susceptible to COVID-19.
Ironically, Kerala seems to be paying the price for the effective control measures that were being adopted. The 100% compliance and cooperation shown by the public in adopting universal masking and other COVID-19 protocols ensured that disease transmission remained slow and steady in the community.
Given the nature of the infection and the current sero prevalence rate in the community, Kerala’s engagement with COVID-19 is going to be a long affair. Cases will continue to occur, with occasional local outbreaks, necessitating stronger control measures. All non-pharmacological means of COVID-19 control — masks, hand sanitation, physical distancing — will have to be maintained strictly.
As the State goes through the agony of the extended epidemic, the real challenge for Kerala in the coming months would be devising strategies to keep the mortality rate down. However, no discussions on this seems to have come up in any public fora.
The government has demanded that the State be given for the COVID-19 vaccination drive.
