Should the study by Banaras Hindu University (BHU) researchers on the adverse effects of Covaxin cause concern? The researchers reported the findings of a one-year follow-up of Covaxin recipients in Drug Safety, a peer-reviewed medical journal. The study covered 635 adolescents and 291 adults who received the vaccine between January 2022 and August 2023. They were interviewed telephonically about specific adverse events after a year of vaccination. Participants reported conditions like alopecia, acne, refractory errors, general weakness, headache and menstrual problems. Serious events including stroke and Guillain-Barre syndrome were reported by a small number of participants.

Should the study by Banaras Hindu University (BHU) researchers on the adverse effects of Covaxin cause concern? The researchers reported the findings of a one-year follow-up of Covaxin recipients in Drug Safety, a peer-reviewed medical journal. The study covered 635 adolescents and 291 adults who received the vaccine between January 2022 and August 2023. They were interviewed telephonically about specific adverse events after a year of vaccination. Participants reported conditions like alopecia, acne, refractory errors, general weakness, headache and menstrual problems. Serious events including stroke and Guillain-Barre syndrome were reported by a small number of participants.

There are some methodological issues. Asking telephonically about the onset of symptoms and their persistence, after a year of the vaccine, is inherently a weak design. The authors admit the limitations due to the lack of background rates of these disorders and the possibility of recall bias. Higher rates are expected in such studies because of ascertainment bias as subjects are more likely to report a side-effect knowing that they are part of this study. However, they can also forget some minor illnesses after such a long period. A shorter contact period, personal interviews, and the use of objective examination of events could have reduced these biases.

The only appropriate way to interpret these numbers is to compare them with the rates for non-vaccinated populations with similar characteristics. That data we do not have, and are unlikely to have as most people are likely to have been vaccinated with some vaccine and those not vaccinated would clearly have different characteristics than those vaccinated. However, the most common symptoms were minor conditions suggesting this is possibly a normal occurrence in this population. Adolescents reported far higher adverse events. This could be due to these disorders themselves being commoner in this age group (menstrual) or more likely to be worried over and reported (hair fall or acne).

The study was conducted after the second wave; by then, almost everyone in India would have been infected by SARS CoV-2. This has implications for interpretation. How does a prior infection modify your response to the vaccine? If an adverse event is seen, then is it due to the earlier infection or due to the vaccine? It is impossible to tell. This is even more important for longer-term side effects. Attributing causality becomes weaker over time as factors other than vaccination play a role. For example, this study reports that post-jab typhoid cases had a higher risk of such symptoms. The possibility of an association being causal is stronger if biological plausibility explains the association. Without knowing how Covaxin could impact menstruation, it is difficult to attribute this to the vaccine. What merits closer scrutiny is that a total of nine adults and one adolescent developed serious adverse events of special interest (AESIs). This is because these are objective measures. However, without a comparison group or background rates, it is not possible to know if these events were linked to vaccination, given the period of study and the study subjects were not “normal” either.

There is no cause for worry now as two to three years have passed since vaccination. This doesn’t mean the authors were wrong to publish now. They had every right to conduct the study and if the journal, after peer review, published it, that is fine too. Long-term safety data must be available as a part of post-marketing surveillance.

Is it wrong for the media to report it? No. But it should be done responsibly. Sensationalism over the issue could have been avoided. Even a balanced report can lead to alarm and anxiety among the public. We are always wiser in hindsight. However, the study does not raise any issue that warrants a review. It is time to move on.

Anand Krishnan is a professor at the Centre for Community Medicine at the All India Institute of Medical Sciences, New Delhi. The views expressed are personal