The first-ever study of Covid infection in Odisha among those fully vaccinated, by Bhubaneswar’s Regional Medical Research Centre (RMRC), an ICMR organisation, has found that around 10% of those reporting a breakthrough infection required hospitalisation.
A breakthrough infection is defined as the detection of SARS-CoV-2 RNA or antigen in a respiratory specimen of a person more than 14 days after receipt of all recommended doses of an approved Covid-19 vaccine.
The preliminary study, yet to be peer-reviewed, was conducted during March 1 and June 10 with nasopharyngeal swab and serum samples from 274 fully vaccinated healthcare and other workers found that 9.9% required hospitalisation with no significant difference between Covaxin and Covishield recipients. Around 83.2% were symptomatic.
Of those, 274 samples (186 male, 88 female) who were found to be positive after 14 days of receiving both the doses, 35 had received Covaxin and 239 Covishield.
Anecdotal reports from India and published reports from USA show that breakthrough infections are rare. In a study in 75 skilled nursing care facilities in Chicago, among 627 persons with Covid infection, only 22 residents and staff members were fully vaccinated. A study done in a Delhi-based hospital among 113 of its fully vaccinated staff found symptomatic breakthrough infections in just 13.3% and only 1 required hospitalisation.
In the Odisha study too, only one healthcare worker died post infection during the study period. The median duration of hospitalisation among the reported cases was 11 days with 1 person still in hospital.
{{/usCountry}}In the Odisha study too, only one healthcare worker died post infection during the study period. The median duration of hospitalisation among the reported cases was 11 days with 1 person still in hospital.
{{/usCountry}}The most common symptoms found was fever (88.5%), followed by cough (77.6%) and sore throat (59.6%). Co-morbidities such as diabetes, hypertension, hypothyroidism and asthma were present in about 64 (23.3%) people.
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Meanwhile, the seropositivity, the production of antibodies in an individual, in people receiving Covishield was 96.7% as against 77.1% in those who got Covaxin jabs.
The authors of the study, however, pointed out two limitations of the study. Firstly, the number of documented vaccination breakthrough cases may be significantly a small fraction of all such cases and secondly, the data is based on passive and voluntary reporting of individuals, and might not be complete representation of breakthrough cases as most asymptomatic individuals or those with mild illness post vaccination may not have got tested.
Noted microbiologist Dr TM Mohapatra, who has worked with ICMR, said the study is consistent with similar studies done for Pfizer and Moderna vaccines.
“The study has once again proved the necessity of taking vaccines to survive Covid infection. In case of a breakthrough infection, hospitalisation may be needed only in case of vaccinated old people with co-morbidities,” he said.
However, he added that the study should have been done for detecting neutralising antibodies in the body rather than spike protein antibodies. “The seropositivity rate of Covishield would naturally be higher as it is made more of a spike protein antibodies that make it difficult for SARS-CoV-2 virus to attach to the cells. Covaxin is a whole virion vaccine and can create more neutralising antibodies. In that respect, the RMRC study has a limited value as the sample size is low and did not check neutralising antibodies for both the vaccines. More studies in different age groups are necessary,” he said.