Two doses of Covid-19 vaccine can help battle breakthrough infections

The two-dose Covid-19 vaccine regimen helps battle “breakthrough infections”, triggered mostly by the highly infectious Delta variant of the SARS-CoV-2. The risk of such infections is higher among healthcare professionals, three separate studies have found.

According to an ICMR estimate, the prevalence of breakthrough infections varies between two to four in 10,000 cases among the general population in India but a new research from the Post Graduate Institute of Medical Education and Research, Chandigarh, shows 16 in every 1,000 fully vaccinated healthcare workers develop such infections.

Breakthrough infections are those cases in which a person gets the Covid-19 infection 14 days after receiving the second dose of the vaccine.

“Among the healthcare workers who received both doses and completed at least 14 days of follow-up after the second dose, the incidence of breakthrough infection was 1.6 per cent (48 of 3,000 health care workers),” the PGI researchers said in a brief communication published in the New England Journal of Medicine.

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This is India's biggest survey of breakthrough infections on healthcare workers, who are exposed to much higher infection risk.

The study was conducted on 12,248 healthcare workers, 7,170 of whom had received the first dose of vaccine, and 3,650 got the second dose. They received Covishield. The prevalence reported in the PGI study is three times more than such incidences reported by an US study after healthcare workers were inoculated with Pfizer or Moderna vaccines.

In the second study on 63 individuals having breakthrough infections in Delhi, no death was reported although the patients had elevated viral load and high grade of fever lasting for five to seven days. During the subsequent course of illness, neither did the disease worsen (biomarkers were stable) nor mortality was reported, the researchers from the All India Institute of Medical Sciences, here and Institute for Genomics and Integrative Biology stated. Twenty four of them are healthcare workers from AIIMS, Delhi.

The zero mortality, said a researcher, was evidence of the protection offered by the vaccine. Out of 63 patients, as many as 53 received Covaxin while ten received Covishield.

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The third study conducted by scientists at IGIB and the National Centre for Disease Control, Delhi has demonstrated that the Delta variant of SARS-CoV-2 (B1.617.2) is capable of very fast rising outbreaks with vaccination breakthroughs as seen in Delhi.

They showed a higher breakthrough risk of Delta compared to Alpha (B1.1.7) that was the second most common variant found in Delhi but it was not associated with breakthrough cases. The Delta variant has now become the dominating strain in most parts of India.

Despite such risks, only 68.5 lakh healthcare workers received two doses of the vaccine even after five months, according to the Union Health Ministry.