A small-scale study on 113 healthcare workers who had received at least one vaccine dose at a private hospital in Delhi found that 18 tested positive for Covid but all except one had mild symptoms
The study, published in the peer-reviewed journal Diabetes and Metabolic Syndrome: Clinical Research and Reviews on May 3, was conducted on employees of the Fortis Centre of Excellence for Diabetes, Metabolic Diseases and Endocrinology in Delhi.
The participants in the study by researchers at Fortis, National Diabetes, Obesity and Cholesterol Foundation, and Diabetes Foundation (India), New Delhi, included doctors, nutritionists, nurses, paramedical workers, and maintenance staff.
Of the 113 in the study, 107 had received the second dose of the vaccine.
Taken in percentage form, the study found that breakthrough infections -- Covid infection in vaccinated individuals -- occurred in 15.9 per cent (18 persons) of the vaccinated individuals and 95 per cent had mild symptoms. Of these, 17 incurred the infection after the second dose and one person.
Except one person who required hospitalisation, all others had mild COVID-19 disease, the researchers said.
According to the study, of the breakthrough infections in 18 persons, 17 incurred the infection after the second dose. These 17 had got their second dose after a mean of 34.8 days following the first jab.
All were symptomatic with fever and half of them had sore throat and cough.
The study covered 123 employees 75 males, 48 females with mean age 42 -- 113 of whom were vaccinated. Of them, 28 people had received the Covaxin vaccine from Bharat Biotech, and 85 the Covishield preventive from the Oxford/AstraZeneca stable.
Covishield, Covaxin and Sputnik V are the three COVID-19 vaccines currently approved for use in India. The three vaccines claim efficacy of 81 per cent, 70 per cent, and 92 per cent respectively. However, Sputnik V has not yet hit the market.
The researchers noted that breakthrough infections after adequate vaccinations are a matter of concern but adequate data on these infections is not available.
Vaccines have effectiveness risk of getting COVID-19 infections by 70-90 per cent, and also shield from severe infection. It is possible, therefore, some people who are fully vaccinated against COVID-19 may get COVID-19 infection, the authors of the study said.
They explained that unpublished data from India as well as published reports from other parts of the world indicate these infections are occurring but are rare.
In addition, it appears that these breakthrough infections are either asymptomatic or mild in nature, the authors added.
The authors acknowledged some limitations of their study: its small sample size, and absence of data on obesity and co-morbid diseases which are important determinants of severity of COVID19. They also did not test asymptomatic infections.