The study was conducted amid several reported cases of infections after partial or complete vaccination, occurring in a small percentage of people. Concerns have been raised on the efficacy of vaccination against the mutated variants of Covid-19. 

The study, conducted by Indraprastha Apollo Hospitals, that include 69 symptomatic healthcare workers working at the hospital, who were tested positive for Covid-19 after their vaccination with the Covishield vaccine during the first 100 days of the vaccination drive earlier this year. 

The study analyzed nasopharyngeal samples for genome sequencing, in collaboration with the National Centre for Disease Control (NCDC). 

The study was conducted between January 16 and April 24. 

"Genome Sequencing is the key test to identify the nature of the virus and the variants that may emerge. 

"Currently, this facility is available in only 10 select Government organizations, but such testing facilities are now being increased in the near future by the Government of India," the hospital said in a statement. 

"Amongst 69 people, 51 were fully vaccinated with two doses (73.91 per cent) and the remaining 18 (26.09 per cent) were partially immunized with a single dose, prior to acquiring the infection. 

"The predominant infections occurred from B.1.617.2 lineage (47.83 per cent), followed by B.1 and B.1.1.7 strains. There were only two hospital admissions (2.89 per cent) for minor symptoms, but no ICU admissions and deaths, from this group," said Anupam Sibal, Group Medical Director and Senior Pediatric Gastroenterologist of Apollo Hospitals. 

Sibal claims these findings are significant because more than half of the cohort were found infected with the Variant of Concern (VoC) and still escaped from the severe illness, which could have been a severe event for them without vaccination coverage. 

Variants of Concern are mutated versions of a virus that may spread more rapidly or may cause severe illness and hence notified for global monitoring by the World Health Organization and other multi-lateral health agencies. 

One of the key authors of this study, Raju Vaishya, Senior Consultant, Orthopedics, Indraprastha Apollo Hospitals said, "We noticed that the post-vaccination SARS-COV-2 infections were seen only in a small subset of our healthcare workers. 

"The majority of these infections were minor, despite being caused by the Variants of Concern." 

Since, the doctor said, the immunity in an individual takes some time after the vaccination, therefore it is essential for the vaccinated individual to be extra careful at least two weeks after the second dose of vaccination and even further, by taking universal safety precautions like maintaining social distancing, using face masks, and hand sanitation. 

This study concluded that the prior vaccination in the health care workers offered clear protection from severe disease due to variants requiring hospital and ICU admissions and deaths. 

Indraprastha Apollo Hospitals is a joint venture between the Government of Delhi and Apollo Hospitals Enterprise Limited. Commissioned in July 1996, it is the third super-specialty tertiary care hospital set up by the Apollo Hospitals Group.