One in nine fully vaccinated gets reinfection: study

T V Jayan New Delhi | Updated on June 10, 2021

The symptoms are mild and did not require supplemental oxygen in breakthrough infection cases.

One in nine people who received both doses of the Covid-19 vaccine was found to be reinfected even though the disease was mild, showed a study carried out among healthcare workers working in a tertiary health facility in the capital.

The study by the researchers belonging to the community medicine department at the Maulana Azad Medical College (MAMC) in New Delhi is yet to be peer-reviewed yet a serious pointer towards the increasing risk being faced by healthcare and frontline workers constantly exposed to the deadly virus. The period of observation coincided with the massive wave of the Covid-19 epidemic in Delhi during the April and May months,


For the study, posted on the MedRxiv pre-print server on Wednesday, the researchers collated data from 326 volunteers, primarily doctors and interns from MAMC. They found that 36 of them had an infection despite receiving both doses of inoculation. While 168 subjects received Covaxin, 158 volunteers were immunised with Covishield. The median time of the infection was 46 days after the administration of the second dose. Such infections following a complete vaccination schedule are called breakthrough infections.

Berakthrough infections

Similar studies elsewhere produced varying results. For instance, one study in another chronic care facility in the capital reported breakthrough infections was 13.6 per cent whereas a similar study in a larger cohort of 3,000 healthcare workers, such infections following the complete vaccination was only 1.6 per cent, indicating that the strains involved too matter. Researchers from the All India Institute of Medical Sciences in New Delhi, who studied 63 cases of breakthrough infections, found that 36 of them were found to have been infected with B.1.167.2 (Delta) strain.

“Breakthrough infections represent a major public health challenge in ending the Covid-19 pandemic. Robust surveillance through large-scale epidemiological studies to identify the predictors of breakthrough infection among individuals at risk, and rapid genomic analysis for early recognition of emerging variants of concern that have greater capability of causing breakthrough infections warrant continued prioritization,” said the team by Dr Rajesh Kumar, a faculty at MAMC.

They also found that most breakthrough infection cases (94.4 per cent) were mild and did not require supplemental oxygen therapy. Healthcare workers with past history of natural Covid-19 infection with recovery were 4.5 times less likely to experience a Covid-19 infection after partial vaccination. This could be because recovery attained after an infection is protective against subsequent Covid-19 infection or reinfection in those who received at least one dose of the vaccine, the authors said.

Published on June 10, 2021

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