A survey on post-vaccination symptoms experienced by 5,396 health-care workers in the country who received the COVID-19 vaccine has reported that 66% experienced at least one post-vaccination symptom. However, most of it was mild and self-limiting and for 68% the symptoms did not last over 48 hours. Only 6% spoke of any symptoms that lasted over 48 hours. For 80%, the symptoms did not affect their work the next day of vaccination.
The online survey, conducted between January 29 and February 4, was led by Rajeev Jayadevan, on behalf of the Indian Medical Association, Kochi.
The respondents belonged to all age groups, from 20 years and those above 60 years were 17.5%. They included doctors (85.8%), nurses (6.2%), technicians (1.1%), and others. About 56% were male and 44% were female. The majority (98.3%) received either Covaxin or Covishield.
The survey was an attempt to capture the post-vaccination experience in the real world, outside of clinical trial conditions, so that the public will know what to expect after vaccination, says Dr. Jayadevan.
The survey found that post-vaccination symptoms experienced by 8% of the respondents who had prior exposure to COVID-19 were no different from the symptoms experienced by the majority of respondents who were non-immune. Interestingly, the study found a remarkable linear correlation between age and the post-vaccination symptoms.
Most of the symptoms were experienced by the respondents in the younger age group and the symptoms declined progressively as the age group went up. Older people also had later onset of symptoms and the duration of symptoms in this group was also shorter than in the younger age groups.
Researchers point out that vaccine reactogenicity (common, expected reactions in response to vaccination) is not considered a reliable sign of immune response and, hence, lack of symptoms post vaccination should not be taken as a reduced immune response.
Also, since the survey did not measure post-vaccination antibody response, it could not be ascertained whether this low level of post-vaccination symptoms in the older group is a reflection of immunosenescence (immunosenescence refers to the gradual decline of the immune system as age advances), researchers point out.
The survey also reported that across all age groups, post-vaccination symptoms were more likely among women (74.7%) than men (58.6%). Women also developed symptoms slightly earlier than men and for slightly longer duration too.
Stressing the importance of reducing fear over new vaccines, researchers point out that often unrelated incidental illnesses may get wrongly attributed to the vaccine.
But without knowing the background rates of a disease in a population, a causal relationship between the vaccine and adverse events cannot be established, they say.