There are always speculations that spike may mutate to the level that can render vaccine ineffective. Mutation in any virus is curious to decipher. The mutations occur so commonly in the same molecule but never take place in the receptor-binding area. If it occurs that is the dead-end for any virus and it will be suicidal to it as it can’t enter the host and multiply. The mutation occurs in the non-receptor-binding part of the virus to escape neutralisation by the host defence system (antibodies). What a great gift nature has authorised to these small creatures.
KEY POINTS REGARDING COVID-19 VACCINES:
1) If you look at phase 2 trial of Covaxin it induces mainly th1 immune response rather th2. It means ADE chances are less but we need more data. So we have to wait for phase 3 data.
2) Unfortunately, they (Bharat Biotech) are not able to achieve a particular number (196) of events (active infection in case and controls) required to show efficacy in 24,000 subjects. We have probably missed the second wave.
3) Surprisingly, Pfizer and Moderna vaccines can be given to all and even those who are recovering from the active infection once their isolation is over. There is no recommendation of antibodies testing in this subset. Though waiting for 90 days after acute Covid infection is recommended.
4) Pregnancy is not a contraindication in Pfizer.
5) Pfizer can be given to people above 16 years of age, whereas Moderna can only be given to those older than 18 years. Covaxin claims that they have successfully conducted a trial on people aged 12 to 18 years regarding efficacy and safety. Surprisingly only 14 patients of this age group were recruited. Covaxin is trying to influence policies by patriotic politics, but it has to pass critical analysis.
The writer is Paediatrician at Sir Gangaram Hospital, New Delhi