A single vaccination dose does not provide significant protection against symptomatic or severe Covid-19 infections, according to Durgesh Nandan Jha of a top private hospital in Delhi.
The study examined Covid infections among healthcare workers at Sir Ganga Ram Hospital between March 1 and May 31, 2018, during the devastating second wave.
Dr Ruma Satwik, the research’s principal author, told TOI that their study on vaccination effectiveness discovered that a single dosage provided very little protection against symptomatic infections or any “outcome of concern,” such as the chance of developing severe symptoms or death from Covid-19.
According to the study, the incidence of symptomatic infection was 12.3 percent in healthcare workers who received a single dose of the vaccine (21 days after receiving the shot), compared to 13.9 percent in the unprotected group. Around 2% of the partially vaccinated study individuals suffered moderate to severe illness, and 0.7% required supplemental oxygen therapy following infection with Covid-19. By contrast, 3.3% of unvaccinated healthcare workers got moderate to severe illness, and 1.7% required supplemental oxygen therapy. As these results demonstrate, there was minimal difference in susceptibility to the virus between the two groups.
“Our findings corroborate the findings from Public Health Scotland on single-dose protection against the Delta strain. This is in contrast to the significantly reduced but still significant protection provided by a single dose, as demonstrated in studies conducted by CMC Vellore (50 percent protection) and Public Health England (33 percent protection),” she explained.
The study enrolled 4,296 healthcare professionals who worked at SGRH. Dr Satwik stated that 2,716 of them had received two doses of Covishield, 623 had received a single dose, and 937 had not been vaccinated as of April 30. Twenty others received either Covaxin or Pfizer but were excluded from the research.
Between March 1 and May 31, the doctor stated, 526 out of 4276 (13%) healthcare workers tested positive for Covid-19, with 2% asymptomatic, 82% having mild symptoms, 10% having serious symptoms, and 5% having severe disease. Six healthcare workers died as a result of Covid-19 infection, five of whom were uninfected and one of whom had received only one dose of the vaccine. No fatalities occurred among fully immunised healthcare personnel.
Several healthcare workers, however, became infected and developed symptoms despite being properly vaccinated, the study found. Two doses of Covishield administered at a median interval of 30 days had a 28 percent efficacy against symptomatic infections, a 67 percent efficacy against moderate to severe disease, a 76 percent efficacy against supplemental oxygen therapy, and a nearly 97 percent efficacy against mortality. “Our study demonstrates a two-dose reduction in protection against symptomatic infections. However, it demonstrates that patients who are fully vaccinated have a significant level of protection against moderate to severe sickness, supplemental oxygen therapy, and death,” one of the researchers explained.
The SGRH study’s findings were published in the European Journal of Internal Medicine’s letters to the editor column. Interestingly, the authors noticed that prior infection with SARS-CoV-2 was strongly protective against all outcomes evaluated, with an efficacy of 93% against symptomatic infections, 89% against moderate to severe disease, and 85% against supplemental oxygen therapy. According to the authors, all deaths occurred in previously uninfected people, indicating that prior infection provided more protection than a single or double dosage of the vaccine.
“This data may prove useful in determining vaccine policy. Administrators in countries with acute vaccine shortages may consider early full vaccination coverage, prioritising individuals who have never been affected, prior to the commencement of another SARS-CoV-2 outbreak,” Dr Ambarish Satwik, a vascular surgeon at SGRH and a study co-author, tweeted. Satendra Katoch and Satish Saluja were also authors on the paper.
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