He said that it would be hard to ascertain whether the antibodies, if detected, are because of cross-reactivity with other coronavirus, or even if they have resulted in response to exposure to SARS CoV-2, how long they will last. Reddy also stressed on the importance of post-regulatory-approval monitoring of vaccines—commonly known as post-marketing surveillance in the context of drugs—to spot delayed adverse effects or adverse effects missed by testing. He cited the case of allergic reaction reported for two recipients of the Pfizer vaccine in the US, outside the trial of the vaccine.
While health secretary Rajesh Bhushan, on December 1, had earlier said that the government had never spoken about vaccinating the entire country, at a later press briefing where the recommendations of the National Expert Group on Vaccine Administration (Negvac) were unveiled, the government had said that everybody for whom vaccination is needed would receive it.
Negvac has recommended prioritising some 30 crore Indians, including healthcare workers, other frontline workers, people older than 50 years of age and those with co-morbidties for receiving the vaccine when it becomes available.
Against this backdrop, Dr Reddy endorsed Indian Council of Medical Research chief Dr Balaram Bhargav’s stand that vaccine coverage should target 60-70% of the population.
Clarifying on the herd immunity threshold and its relation to the R0 number—which represents the virus’s reporduction rate or how many persons an infected person would end up infecting—Dr Reddy said that, in the case of SARS CoV-2, the R0 number can, at the very best, be helpful in trend analysis than in arriving at a HIT figure, especially given how distancing, mask-use, etc, affect the R0 figure.