The story so far: The Indian Council of Medical Research (ICMR) has reported that around two to four of 10,000 people given two doses of the COVID-19 vaccine have tested positive for the disease.

• Contracting COVID-19 after vaccination is known as breakthrough infection.
• It has occurred in “a very small number” of people and does not undermine the effectiveness of vaccination.

What is a breakthrough infection?

• These are infections that occur in people who have been vaccinated.
• Such cases are not out of the ordinary as the vaccines that have been approved so far the world over are made to protect against disease and not the transmission of the virus.
• Phase 3 clinical trials conducted before vaccines were approved showed a fairly constant proportion of infections among those vaccinated.
• In the AstraZeneca trial, for instance, 30 out of 5,807 vaccinated — about 0.5% — were symptomatic and tested positive 14 days after the second shot.

How does India compare with others?

• According to data out of the 1.7 million people who got a second dose of Covaxin (and thus fully inoculated), 695 tested positive — a rate of 0.04%.
• Of the 15.7 million who got a second dose of Covishield, 5,014 tested positive, a rate of 0.03%.

Is it rare to get infected even after vaccination?

• The CDC guidelines on breakthrough infections state that all such reported rates are an undercount.
• This surveillance system is passive and relies on voluntary reporting from state health departments which may not be complete.
• Also, not all real-world breakthrough cases will be identified because of lack of testing. This is particularly true in instances of asymptomatic or mild illness.

What are the reasons for such infections?

• Healthcare and frontline workers were getting infected because of their constant high exposure to COVID-19 patients. The other reason was due to “highly transmissible new variants”.
• Studies on the AstraZeneca vaccine show that its efficacy is reduced when faced with the U.K. and the South African variant.

https://www.thehindu.com/sci-tech/health/the-hindu-explains-can-people-test-positive-for-covid-19-even-after-inoculation/article34403519.ece

Download PDF