Accelerate second dose coverage for Covid-19 vaccination, AIIMS study suggests

Fully vaccinated Indians have a significantly lower risk of developing severe Covid-19, says a new real-world vaccine efficacy study carried out by a team at the All India Institute of Medical Sciences, Delhi, underlining the need to rapidly improve the number of fully vaccinated individuals.

Since India began its Covid-19 vaccination drive on January 16, more than 65 crore adults received the vaccines of which 50 crore persons got the first dose while just about 15 crore got the second one.

On Tuesday, for the second time, more than one crore doses were administered within five days. Nearly 53 per cent of 94.47 crore adults have received the first dose of the Covid-19 vaccines so far whereas 16 per cent got both the shots.

But the AIIMS study on nearly 1,750 Covid-19 infected persons adds fresh evidence to a growing list of research papers, each highlighting the importance of completing the two doses as quickly as possible because of the highly contagious Delta variant that drove the second surge besides triggering many breakthrough infections.

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It is also found that while the two doses impart a high level of protection against SARS-CoV-2, those who unfortunately develop the infection due to old age or comorbidity, face the same risk of dying as an unvaccinated person.

“Vaccinated people are protected against severe disease, but it is not 100 per cent. If a few of them go on to develop severe disease they may have a bad outcome. So along with the vaccine, Covid appropriate behavior (like masking or following social distancing norms) is important for high risk groups. Other factors also contribute to the severity of disease,” said AIIMS director Randeep Guleria.

The doctors compared 53 fully vaccinated individuals with 231 who received only the first shot and 1,464 unvaccinated persons. The 53 patients studied were breakthrough infection cases.

A significantly lesser proportion of the individuals with breakthrough infection required oxygen supplementation (18.2 per cent) or ventilatory support (5 per cent) compared to the individuals in the other groups. Very few of these individuals deteriorated (9.1 per cent) or ever progressed to critical illness (4.6 per cent) during their hospital stay compared to other study groups.

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“Three individuals (5.7 per cent) out of the 53 who developed breakthrough infection succumbed to illness while the case fatality rate was significantly higher in the unvaccinated (22.8 per cent) and partially vaccinated (19.5 per cent) groups,” the AIIMS team reported in a preliminary study, which is yet to be peer-reviewed but has been posted online in a medical archive.

A higher proportion of unvaccinated and partially vaccinated patients showed signatures of hyper-inflammatory responses compared to fully vaccinated patients, indicating that vaccination reduces the risk of Covid-19-linked inflammatory responses.

But once the patient developed hypoxia, or oxygen deprivation, or acute respiratory distress syndrome, the odds of developing critical illness or death were similar to those of unvaccinated individuals, it added.