Dr Krishna Reddy Nallamalla
As the second wave of Covid-19 rages across India, the issue of vaccine hesitancy has changed to one of vaccine urgency. The demand for vaccines is outpacing the supply across the country. At the same time, concerns on unusual blood clots being reported with the Astra-Zeneca Covishield vaccine are increasing among the lay public. Moreover, some people are reporting getting infected even after receiving two doses of the vaccine. There is a real risk of hope turning into despair, if things are not put in right perspective.
The Covid-19 vaccines’ efficacy rates in preventing the Covid illness vary from 60 percent to over 90 percent. That means 10-40 percent of people who have been vaccinated can still develop the illness if they do not continue to practice Covid appropriate behavior of face masking, hand washing, and social distancing. However, vaccines are more than 90 percent effective in preventing moderate to severe illness. That way even if vaccinated people do get infected, they will either be asymptomatic or mildly symptomatic. Hence, post-vaccination infections should not cause people to lose faith in the vaccines.
People are also becoming aware about the Covid variants. They are now familiar with the UK, South Africa, and Brazil variants, among others. Knowledge about the double mutant Indian variant (B.1.617) will also become common knowledge soon. It is important to understand that it is natural for viruses to mutate. Some of these mutations confer advantages like evading the preexisting immunity or facilitating easy entry into human cells or becoming resistant to anti-viral drugs. If a variant,capable of evading vaccine induced immunity, is circulating within the population, people can get infected despite being vaccinated. The South Africa variant and the Brazil variant are understood to evade the immunity developed after the Astra-Zeneca Covishield vaccine or from infection with the original virus strain. This is another reason why people must continue with their Covid appropriate behavior until the pandemic is eradicated or controlled across the world.
It is still not clear as to how long the immunity after both natural infection and vaccination lasts. The immunity following a common cold Corona virus is known to last less than 12 months. The Covid-19 pandemic has crossed the one-year milestone. Ongoing surveillance systems will keep throwing light on the duration of immunity following natural infections and following vaccination. They will also investigate the variables that influence the duration of immunity. These may be related to host factors such as age, gender, severity of illness (asymptomatic to severe), host immunity status, intake of immune boosters and suppressants, the nature of the vaccine, or the nature of the viral mutations, among others.
Given the above facts, people should not let their guard down, even for a day, and continue face masking, hand washing, and social distancing.
Dr Krishna Reddy Nallamalla
Country Director, ACCESS Health International