Corona Daily 127: Breakthroughs

Last week, I wrote about a doctor friend who got infected after being fully vaccinated. Such infections are called “Breakthrough infections”. Not breakthroughs for scientists, but for the virus. As if it has managed to break through the vaccine protection. The Hepatitis B virus that infects one after inoculation is called the “vaccine escape mutant”.

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 One immunologist clarifies: Being vaccinated doesn’t mean you are immune. It means you have a better chance of protection. Vaccine is just one variable in the toolbox available for protection. The goal of vaccination is not eradication of covid, and this may surprise many. The goal is to peacefully coexist with the coronavirus, like we do with flu. Of course, eradication would be nice, but at present that is considered too ambitious.

A breakthrough infection can happen in immuno-compromised people. Age and weight of a person can matter. Doses for flu vaccines differ based on such factors. However, for covid vaccines, an identical dose is given to everyone. This may prove to be insufficient or excessive. The good news is that most cases noticed so far have milder symptoms and a shorter duration.

Virus mutations can be a reason. So far, the main approved vaccines – Pfizer, Moderna and AstraZeneca are working against all variants. (A single exception was AstraZeneca not working in South Africa against the locally identified variant). Ideally, every breakthrough case should be subjected to genomic surveillance. A fully vaccinated person’s positive sample should go for a genome analysis. That will tell us exactly which variants are more successful in escaping the vaccine effect. Unfortunately, such data is not available.

Large viral loads may cause infection. If a fully vaccinated person attends a superspreader event or joins a crowd where the virus is rampant, he or she can get infected because of the sheer viral load. Even in that case, the symptoms are likely to be mild.

Improper storage of the vaccine can be a reason. This is rare. However, in a country like India with unstable power supply, it is a challenge to maintain an uninterrupted vaccine cold chain. Vaccines lose potency if stored at wrong temperatures or used after an expiry date. Moderna allows anyone to check online the expiry date of its vaccine based on the batch number.

Some of those testing positive after vaccination are asymptomatic cases. Including them is a bit unfair. In most vaccine trials asymptomatic cases were excluded. Immunologists distinguish between infection and disease. Whenever someone tests positive, the real question is, are they sick, and how sick are they? They may still be isolated for the benefit of others. But in all likelihood, their asymptomatic infection is a successful outcome of the vaccine.

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USA has already administered 66 million doses. The data of breakthrough infections has started trickling in. Based on the state-wise data I have seen so far, one person out of 10,000 can get infected despite being vaccinated. This is excellent news, because it means 9,999 out of 10,000 are protected.

A study published this week in the New England Journal of Medicine offers another piece of good news. The research found that fully vaccinated people have robust levels of antibodies more than six months later. Those levels subside very slowly, giving hope that the vaccine immunity may last for a long time. The study included mainly those who received Moderna, and it is hoped similar studies will show similar results for other vaccines.

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Breakthrough infections are bound to happen. But they shouldn’t stop anyone from getting vaccinated. One doesn’t stop wearing a helmet just because some biker had an accident wearing it.

At the same time, it is important to track the breakthrough data, to look at the percentage and analyse virus variants where possible. If such infections were to climb to unexpectedly high rates, an additional booster shot or tweaking of the vaccine may be needed to improve the immune response.

Ravi