Two doses of COVID-19 vaccine offer high protection against infection and hospitalisation, finds a study. The study carried out at CMC Vellore has found that two-doses of COVID vaccine is effective even among health-care workers who have a high risk of being infected.
While the study found vaccination to be protective, it did not investigate the proportion of cases caused by the beta (B.1.1.7) and delta (B.1.617.2) variants that were responsible for the second wave.
Quoting Dr. Joy J Mammen, Professor at the Department of Transfusion Medicine, CMC Vellore and the corresponding author of the study, a report by The Hindu 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," the report quoted Mammen saying
Dr Mammen also said that they were not able to individually study the efficacy of Covishield and Covaxin as only a few received Covaxin.
In total, 8991 (84.8%) health-care workers were vaccinated between January 21 and April 30 2021. A majority of them (nearly 8,400) received Covishield. The team studied the incidence of infection and hospitalisation between February 21 and May 19.The team found that not a single death reported among the 8,958 vaccinated individuals, while there was one death among the 1,609 unvaccinated health-care workers.
The study found that among the 7,080 health-care workers who received two doses, the vaccines offered 65% protection against infection, 77% protection against hospitalisation, 92% protection against the need for oxygen and 94% protection from ICU admission. Among the fully vaccinated individuals, infection was seen on average 47 days after the second dose.
The study also found that even a single dose of COVID-19 vaccine offered significantly high protection against both infection and hospitalisation. In 1,878 health-care workers who received only one dose, protection against infection was 61%, while protection against hospitalisation was 70%.
In the case of those needing oxygen care and ICU admission, the protection offered by a single dose was 94% and 95%, respectively, says the report
Among the 1,878 health-care workers who received only one dose, 200 (10.6%) were infected, while only 22 (1.2%) needed hospitalisation. In comparison, among the 7,080 health-care workers who received two doses, 679 (9.6%) were infected while 64 (0.9%) needed hospitalisation. Among those who received two doses, only four needed oxygen support and just two needed ICU care.
Among the 1,609 health-care workers who had not received any vaccination, 438 (27.2%) got infected, while 64 (4%) needed hospitalisation, says the report quoting the study. The study also found that Eleven (0.7%) individuals who did not get any vaccine needed oxygen support and eight (0.5%) needed ICU care.
According to the authors, the reason why many health-care workers were not able to take the second dose was due to vaccine shortage and subsequently due to changes in guidelines on the interval between the first and the second dose of Covishield.
The study which has been posted on a preprint server is yet to be peer-reviewed.