Medical workers tend to a patient suffering from COVID-19 in Holy Family Hospital, New Delhi, April 29, 2021. Photo: Reuters/Danish Siddiqui
New Delhi: In yet another sign that vaccines are the only safe and effective way to end the pandemic, a study conducted by the Christian Medical College (CMC) in Vellore found that COVID-19 vaccines are highly effective in preventing symptomatic infections and hospitalisation among healthcare workers – who are at a higher risk of being infected.
The study, presented through a preprint paper found that one dose of vaccine offered 61% protective effect against infection, while two doses offered 65%. Significantly, one dose reduced the risk of hospitalisation by 70% and two doses by 77%.
Among the staff members who received vaccines, no deaths were reported. Only one staff member of CMC has died since the pandemic began, and that person had several comorbidities and did not receive the vaccine, the study says.
The authors say they were not able to study the efficacy of Covishield and Covaxin or what proportion of cases were caused by the variants which filled the second wave in India.
The CMC study involved the observation of nearly all of its 10,600 employees. According to the study, 8,991 staff members (84.8%) were vaccinated between January 21 and April 30. A majority (93.4%) received Covishield, the Oxford-AstraZeneca vaccine, and the remainder received Covaxin. The study reports the incidence of symptomatic COVID-19 infection among the workers between February 21 and May 19.
Among the 7,080 health workers of CMC who were fully vaccinated, just 679 (9.6%) developed an infection. “The risk of infection among fully vaccinated HCWs was significantly lower when compared with unvaccinated HCWs,” the study notes.
“The protective effect of vaccination in preventing infection, hospitalization, need for oxygen and ICU admission were 65%, 77%, 92% and 94% respectively,” the study says. In the case of workers who received just one dose of the vaccine, the corresponding protective effect was 61%, 70%, 94% and 95%, highlighting the fact that even a single dose of vaccine is significantly effective.
“The median time from first dose to development of infection was 77 (62-89) days and coincided with the second peak in India during April and May 2021. Thirty-three HCWs developed infection within 2-weeks of the second dose of vaccine,” the study says.
Some CMC health workers could not take the second dose initially due to vaccine shortage and subsequently due to the change in guidelines which mandated a 12-16 week interval between doses of the Covishield vaccine, the study says.
Among the 1,609 healthcare workers who did not receive any dose of the vaccines, a significantly higher proportion – 27.2% – were infected. A higher proportion (4%) also needed hospitalisation.
Joy J. Mammen, professor at CMC’s Department of Transfusion Medicine the corresponding author of the preprint, told The Hindu, “Our study shows that COVID-19 vaccines have a great benefit in reducing infection and severity of disease. Vaccination helps in breaking the chain of transmission.”
Gagandeep Kang, who also works at CMC but was not involved in the study, also tweeted the paper and said it shows vaccines are working well, especially in preventing severe disease.
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, led by @joy_mammen. Next step, study protection against variants. 😀https://t.co/6i6jQiY7OS
— G Kang (@GKangInd) June 11, 2021
“Beyond the immediate, implications for public health include cost-effective protection from infection, reduction of illness severity and an intervention to break the chain of transmission effectively. Even as many states chose to restrict movement to reduce stress on the healthcare system, we realize that future waves can at best be prevented or at worst mitigated through aggressive and widespread vaccination,” the authors say.
The authors note that their study corroborates the findings of others such as those conducted in the UK, Jerusalem and California that vaccination is protective. The UK study found that asymptomatic infections occurred in 3.8% of vaccinated healthcare workers 38% of those who were unvaccinated.The California study showed that only 37 healthcare workers who received two doses of the vaccine tested positive for COVID-19.
Another study conducted by Apollo Hospitals in India, which covered 3,235 healthcare workers, found that 85 were infected by the virus during the period of observation.
The hospital’s group medical director Anupam Sibal said, “Our study demonstrated that 97.38% of those vaccinated were protected from an infection and hospitalisation rate was only 0.06%. The results of the study show that break-through infections occur only in a small percentage and these are primarily minor infections that do not lead to severe disease. There were no ICU admissions or death. Our study makes the case for vaccination stronger.”
At the Apollo Indraprastha Hospital, the Delta variant (B.1.617.2) of the coronavirus was detected in nearly half of the samples of 69 healthcare workers who had received either two or one doses, suggesting that it is ‘less sensitive to vaccines’.