The Delta variant of SARS-COV-2 was behind majority of clinical cases of breakthrough infection of COVID-19 but only 9.8 percent cases required hospitalisation and fatality was observed in only 0.4 percent cases, according to a new ICMR study.
Breakthrough infections are those cases where a person gets infected even after getting vaccinated.
The ICMR study, the largest and first nationwide study on post-vaccination breakthrough infections in India, said its analysis shows that the vaccination does provide a reduction in hospital admission and mortality.
"Therefore, enhancing the vaccination drive and immunising the populations quickly would be the most important strategy to prevent further deadly waves of the COVID-19 and would reduce the burden on the health care system," the study said.
The study conducted by Pune’s National Institute of Virology (NIV) involved a sample size of 677 people – all cases of breakthrough infections. Out of them, 482 people or 71 percent of the cases were symptomatic with fever being the most dominant and consistent symptom, 71 people or 9.8 percent of them required hospitalisation, and three vaccinated persons died during the second wave.
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Two new SARS-CoV-2 variants Delta AY.1 and AY.2 were also identified in these study samples.
"Delta AY.1 and AY.2 is characterized by the presence of K417N mutation in the spike protein region. K417N, E484K, L452R, and E484Q are the mutations known to disrupt receptor binding domain (RBD) binding capacity and make them more infectious by immune escape mechanisms against the current vaccines. This indicates improved virus fitness to evade immune responses and survive against the vaccines," the study said.
This study indicated that the majority of the clinical cases in the breakthrough were infected with the Delta variant and only 9.8 percent cases required hospitalization while fatality was observed in only 0.4 percent cases.
"The overall majority (86.09 percent) of the breakthrough infections were caused by the Delta variant (B.1.617.2) of SARS-CoV-2 in different regions of India except for the northern region where the Alpha variant predominated," the study said.
The present study revealed the infection among breakthrough cases predominantly occurred through Delta variants indicating its high community transmission during March-June followed by Alpha and Kappa variants.
In the study, 67 cases (9.8 percent) required hospitalization and fatality was observed in only three cases (0.4 percent).
The 17 states and Union Territories from where the samples were collected are Maharashtra, Kerala, Gujarat, Uttarakhand, Karnataka, Manipur, Assam, Jammu and Kashmir, Chandigarh, Rajasthan, Madhya Pradesh, Punjab, Puducherry, New Delhi, West Bengal, Tamil Nadu, and Jharkhand.
The study found that southern, western, eastern, and north-western regions of India predominantly reported breakthrough infections from mainly Delta and then Kappa variant of SARS-CoV-2.
Out of the 677 patients analysed, 85 acquired COVID-19 infection after taking the first dose of the vaccine, while 592 were infected after receiving both doses of the vaccine.
A total of 604 patients had received Covishield vaccine, 71 had received Covaxin and two had received Sinopharm vaccine.
A total of 482 cases (71 percent) were symptomatic with one or more symptoms, while 29 percent had asymptomatic SARS-CoV-2 infection.
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