Most countries around the world have started giving booster doses to already vaccinated people. Its entry into India slowed down due to the huge population. Giving 2 doses of vaccines to each of the Indian citizens was in itself a challenging task. Then there was a problem of giving conventional Oxford-Astrazeneca vaccines to children. Also, as most of the vaccines were given late, after the 2nd wave, the herd immunity for Covid-19 persisted amongst the masses. But now, at the turn of the new year, most vaccines have become ineffective due to ageing, and require a boost up using the 3rd dose. The beginning of the third wave, from the last week of December, sparked the 3rd dose vaccination drive for adults and the indigenous Covaxin drive for children.
The main question is, how are people getting affected after receiving two doses of vaccination. There can be two causes, one is that the vaccines are not effective against the new variants, and the other one is that the immunity due to the vaccine has gone down. The second cause is the most probable, as the vaccines are known to be effective against the new dominant strain, Omicron. A Lancet study has found that immunity against Covid-19 by Oxford-Astrazeneca vaccine wanes after 3 months of receiving the 2nd dose. Researchers found that immunity declines after 3 months when the chances of hospitalization and dying doubles than that of two weeks after receiving the 2nd dose. The study was conducted on 2 million citizens of Scotland and 42 million citizens of Brazil who have taken the Oxford-Astrazeneca vaccine.
The chance of hospitalization becomes thrice after 4 months and 5 times after 5 months of vaccination. However, other vaccines like Pfizer and Moderna shows much slower rates of ageing. A booster dose is needed after 5 months to boost up the immunity against Covid-19. Latest studies found that the booster dose of Oxford-AstraZeneca, Pfizer and Moderna is significantly effective against the new Omicron variant. Currently, due to the large population, as well as a scarcity of vaccines in the country, the interval between 2nd and booster 3rd dose of Covishield is now pegged at 39 weeks by the Indian Government.
The waning of immunity is the prime cause of the sudden rise in Covid-19 cases in India post-Christmas. The year-end celebrations around the country were followed by the advent of the third wave of Covid-19. Delhi, Mumbai, Kolkata, Chennai and other big cities have already witnessed partial lockdowns and restrictions to curb the spread of Covid-19. The booster dose and Covaxin for children have been made available. Currently, the booster shot is being given only to doctors, health workers and people above the age of 60. Keep updated on the 3rd dose availability and get vaccinated as soon as it is available to you.
Written by – Himadri Paul