Covid risk low in inoculated health staff: Study
NEW DELHI: Vaccines against coronavirus disease protect against severe disease and death, shows a study by Christian Medical College, Vellore, that found 9.6% of completely vaccinated health care workers contracted the viral infection as against 27.2% of those who were unvaccinated.
Of those who did get the infection after completing a 14-day period following both doses of the vaccine, only 0.9% were hospitalised as compared to 4% among those who were unvaccinated. Fewer patients needed oxygen support and admission to the intensive care unit among those vaccinated as compared to the unvaccinated group. Among the completely vaccinated individuals, only 0.06% needed oxygen therapy and 0.03% had to be admitted to the ICU. In comparison, 0.7% of the unvaccinated individuals needed oxygen therapy and 0.5% needed ICU care.
“Vaccines are working well! Good against infection (in healthcare=high transmission), great against severe disease. Here is the 1st data from healthcare workers at @Offcmcvellore …. Next step, study protection against variants,” vaccine expert and professor of microbiology at the institute Dr Gagandeep Kang said in a tweet.
The incidence of infection among the fully vaccinated health care workers is higher than what has been reported in other hospitals from India and abroad. While Chandigarh’s Postgraduate Institute of Medical Education and Research (PGIMER) reported 1.6% infections in fully vaccinated individuals, Delhi’s Indraprastha Apollo hospital reported a figure of 2.62%.
According to the CMC study yet to be published in Mayo Proceedings, a study of 23,324 health care workers from the UK showed 3.8% got infected among those vaccinated and 38% among the unvaccinated.
Infection occurred in 6.9% of the vaccinated health care workers, according to a study from Jerusalem.
However, a study from a Delhi hospital that has been treating only Covid-19 patients for over a year saw an 11% infection rate in vaccinated health care workers. The researchers of the study say that the higher rate of infection was likely a function of exposure to the virus among health care workers and the severe surge of cases with the Alpha and Delta variants in April and May.
“We realise that future waves can at best be prevented or at worst mitigated through aggressive and widespread vaccination,” the Cmc-vellore study concluded. The study reported that among people who tested positive during the study’s duration – vaccinated and unvaccinated – the female to male ratio was 3:2 and the median age for infection was 33 years. Most of the infections also happened in April coinciding with the surge in cases of Covid-19 across the country.
The study acknowledged a shortage of vaccine doses could have led to many not getting their second shot. “Some health care workers (17%) could not take the second dose, initially due to vaccine shortage and subsequently despite vaccine availability, due to changes in guidelines on the interval between doses,” the study said.
“No vaccine is 100% effective, but several studies have shown that the vaccines offer close to 100% protection against severe disease and deaths. To my mind, the report from CMC Vellore is one of the best studies to come out of India so far; it is very systemically done and shows that the need for hospitalisation, ICU care, and oxygen support was also less among those vaccinated,” said Dr GC Khilnani, chairman of PSRI Institute of pulmonary and critical care and former head of the department of pulmonology at the All India Institute of Medical Sciences.
He added, “What the CMC study also shows is that the number of infections was higher among those who had received just one dose in comparison to those who got both the doses. So, the previous thought that one dose of Covishield can offer sufficient immunity is not true.”
A recent pre-print study from the National Institute of Virology shows that the neutralisation titre of Covaxin reduced 2.7 fold with the Delta variant in circulation in Delhi during the April-may surge. Lower antibodies, however, does not mean that a person is not protected.