Vaccines Working Against Covid-19, Two Doses Reduce Need for Oxygen Therapy: Study

A new study conducted by Christian Medical College (CMC) in Vellore has found that two doses of Covid-19 vaccine helped to reduce hospitalisation, need for oxygen therapy and ICU admission among healthcare workers (HCWs) who have a high risk of being infected with novel coronavirus. The study, however, also mentioned that it did not examine the beta (B.1.1.7) and delta (B.1.617.2) Covid-19 variants that were responsible for the second wave in the country.

As per the research team, the CMC Vellore with 10,600 employees, vaccinated 8,991 staff between January 21 and April 30. A majority (93.4%) received Covishield manufactured by Serum Institute of India (SII) and the rest received Bharat Biotech’s Covaxin. “The risk of infection among fully vaccinated HCWs was significantly lower when compared with unvaccinated HCWs. Similarly vaccination with two doses reduced hospitalisation (RR 0.23;95%CI 0.16-0.32), need for oxygen therapy (RR 0.08; 95%CI 0.03-0.26) and ICU admission (RR 0.06; 95%CI 0.01-0.27).”

Dr Joy J Mammen, Professor at the Department of Transfusion Medicine, CMC Vellore is the corresponding author of the preprint.

The protective effect of vaccination in preventing infection, hospitalisation, need for oxygen and ICU admission were 65 per cent, 77 per cent, 92 per cent and 94 per cent respectively, the study found.

“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,” tweeted vaccine expert Dr Gagandeep Kang along with the study paper.

The study further revealed that fully vaccinated individuals, however, did contract the infection, with 679 (9.6%) contracting it within 47 days (34-58) following their second dose, and 33 individuals contracting Covid-19 within two weeks of the second dose.

“The only staff member who died since the beginning of the pandemic had multiple comorbidities and had not taken the vaccine,” it mentioned.

“Subgroup analysis on the efficacy of the two vaccines was not possible due to few HCWs receiving Covaxin. Some HCWs (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,” as per the authors of the study.

Citing the examples of other countries which conducted studies and revealed that vaccination is protective, the CMC Vellore said, “A study of 23,324 HCWs in the UK, 2 reported vaccine coverage of 89%. During the 2-month follow up, symptomatic and asymptomatic infections occurred in 80 participants (3.8%) among vaccinated and 977 (38%) among unvaccinated. In a study from Jerusalem, infection occurred over 2-months in 366 (6.9%) of 5297 vaccinated HCWs and 213 of 754 unvaccinated individuals. A third study from California (n=28,184), showed that only 37 HCWs who received two doses of the vaccine tested positive. Our study corroborates these studies that vaccination is protective, although we did not look at the variants responsible for the massive second wave.”

“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,” it added.

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