What science tells us about Covid-19 vaccines

According to science, immunity sets in around two weeks after the second dose, although research recommends delaying the second dose in the case of the Covishield vaccine (the Indian version of the Oxford/ AstraZeneca vaccine) by 6-8 weeks to maximise immunity.
A nurse prepares the Covid-19 vaccine in Los Angeles, California. -(AFP)
A nurse prepares the Covid-19 vaccine in Los Angeles, California. -(AFP)
Updated on Apr 03, 2021 07:10 AM IST
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By R Sukumar, Hindustan Times, New Delhi

Re-infections, infections after vaccine shots, prevention of transmission – the Indian medical and scientific space is beset with conflicting information regarding Covid-19 and the vaccines meant to stop the virus’s march, with some originating from the very people who should be shedding clarity on the issues. On Thursday, April 2, HT and some others published details of a study conducted by scientists from the Indian Council of Medical Research that suggested a 4.5% re-infection rate, but without analysing the genomes of the first and the second infections. These may not have been readily available – despite a surge that is most likely caused by so-called VOCs, or variants of concern, especially in Maharashtra, India is not sequencing as many viral genomes as it should, nor even as many as it promised to when variants became a matter of concern. The number is also much higher than what most international studies suggest – a reinfection rate of under 1%. Indeed, if the reinfection rate is 4.5%, as indicated by the study, then the house is already on fire.

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There are also some reports, likely true, of doctors who have received two doses of the vaccine, as prescribed, contracting Covid-19. According to science, immunity sets in around two weeks after the second dose, although research recommends delaying the second dose in the case of the Covishield vaccine (the Indian version of the Oxford/ AstraZeneca vaccine) by 6-8 weeks to maximise immunity. That means these people should have been immune. How, then, did they get infected?

Data put out by the companies behind the two vaccines in use in India (Bharat Biotech is the second) claim an efficacy of 70%-80% in preventing infections. Taking the lower end of the range, let’s assume the vaccine is effective in 70% of cases. What does this mean? It means 70% of those vaccinated will not be infected. Conversely, three of every 10 people who have received vaccines may be, and that is likely what is emerging, especially as the rate of infection itself speeds as the intensity of the second wave of infections in India becomes stronger. But both vaccines are also, based on their makers’ claims, 100% effective in preventing severe disease and death. This means no one who gets the vaccine will die from Covid-19. Low as India’s case fatality rate is, this is still a relief.

Science isn’t very clear on whether those vaccinated could still carry the virus even if they don’t get infected themselves, and whether they can then pass it on to others. The answer is likely yes, which means that the vaccines probably do not offer any protection against transmission. This is important to understand – especially in a country where even the announcement of vaccines was met with a collective exhalation of relief and rapid abandonment of all Covid-safe behaviour. There were a few rash statements by health administrators at the beginning of the vaccine drive that the shots prevent transmission, but they do not.

Finally, there’s been some confusion on Adverse Events Following Immunisation (or AEFI) as it is called. The Economic Times reported on Friday that six of the 13 AEFI cases studied by the national committee looking at these showed a “consistent causal” relationship with the vaccination, a finding that has set alarm bells ringing in various quarters. But the report also adds that none of the cases were caused by the vaccine itself. Clearly, more clarity is needed (the committee studied 13 cases till March 9). Till then, it makes sense to look closely at the numbers. There were 79 deaths till March 13, according to a report in The Hindu. India had administered 29.19 million doses of the vaccine till that day (18.56 million had one dose and 5.21 million both doses). So, these 79 deaths need to be seen in the context of the 24 million people vaccinated. Which means, 99.9997% of the people who take the vaccine have no reason to fear.

So, what do the vaccines do? They prevent death and severe disease in all cases, infections in the majority of cases, and perhaps do not have any bearing at all on transmission. This is what science tells us as of today, April 2. If there is an update, you will read it here. Meanwhile, take the jab.

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Monday, October 18, 2021