BENGALURU: Despite a difference in efficacy level, all vaccines are effective against Covid-19, and any vaccine is better than no vaccine, say doctors. Indian studies say that Covaxin is better than Covishield, though their efficacy is similar. However, these studies are limited.
Those travelling abroad are better off taking Covishield, which is approved by several countries, said Dr Subrata Das, Senior Consultant, Internal Medicine & Diabetology, Sakra World Hospital. “They all act in different modalities with the end goal of triggering immunity. They could be composed of a part of the virus, the whole inactivated virus, RNA of the virus, etc. Storing the Pfizer vaccine will be difficult in India as it has to be maintained at -15 degrees to -18 degrees Celsius. Russian studies show over 90 per cent efficacy for the Sputnik vaccine.”
Those who have a history of thrombosis (blood clots), stroke, heart attack must take a non-Covishield vaccine, he adds. There is no need to check antibody levels after taking the vaccine, as some vaccines evoke T-cell immunity (long-term memory of the immune response). Studies against variants are limited, though companies claim effectiveness against them. We still don’t have real-world data on this and need more time, Dr Das explained.
“On the ground, there is no major difference in efficacy. If we are looking at severity of the disease, mortality and hospitalisation, the vaccine is effective after taking both doses. Respiratory issues such as low oxygen are visible even after a person takes one dose,” said Dr Anoop Amarnath, Head, Scientific Board and Chairman-Geriatric Medicine, Manipal Hospitals, and member of the state’s Critical Care Support Team.
These vaccines were trialled in the first and second wave, hence, their effectiveness against variants is yet to be studied. There is not much data, and the Covid-19 vaccine may be similar to the Influenza vaccine, in that the composition might change as per prevalence of the strain, Dr Amarnath added.
“Primary efficacy data in both Covaxin and Covishield show they prevent moderate to severe disease with a rate of 65 per cent to 80 per cent. How much they diminish over time has not been studied yet. Sputnik reported 85-90 per cent efficacy, while Moderna and Pfizer have reported over 90 per cent, with the percentage falling to 40-70 per cent,” said Dr Ravindra Mehta, Senior Consultant, and HoD, Pulmonology and Interventional Pulmonology, Apollo Speciality Hospital