Officials said that a “small” fraction of those vaccinated with either Covaxin or Covishield have tested positive. However, these instances of “breakthrough” infections do not undermine the efficacy of the vaccines.
“These vaccines definitely, definitely protect against disease. However, the immune response begins to develop usually two weeks after every dose and there are variations within individuals, too. Even after the first dose, if exposure to the virus happens, one can test positive,” said Dr. Balram Bhargava, Director General, Indian Council of Medical Research (ICMR).
Of the 9.3 million who received the first dose of Covaxin, 4,208 tested positive; and of the 1.7 million who received the second dose, 695 tested positive.
For Covishield, of the 100.3 million who received the first dose, 17,145 tested positive; and of the 15 million who got the second dose, 5,014 tested postive.
Two key reasons for this, according to Dr. Bhargava, were that healthcare and frontline workers, who were among the first to be vaccinated, were as a population far more exposed to the virus and therefore more susceptible. Secondly, the emergence of “the highly transmissible second wave (newer variants) ” may have contributed to instances of infection among those vaccinated.
Several variants, which have mutations that have been shown to avoid detection by the immune system, and in some cases reduce the efficacy of vaccines, have been reported globally, including in India.
“This is roughly around 2 in 10,000 and is a very, very small fraction. We have seen similar rates of reinfection internationally too from the use of other vaccines,” Dr. V.K. Paul, Chairman, NEGVAC (National Expert Group on Vaccination), the committee that oversees the COVID-19 management strategy.
When comparing patterns of infection and mortality in the first and second waves of the pandemic, a slight percentage increase in cases among those in the 10-20 years age group is seen in the current wave — 8.5% compared to 8.07% earlier. There is an increase in cases among those in the 40-70 years age group from the previous wave, and the same fraction of those in the 30-40 years age group persists.
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In terms of deaths — that is now nearly 2,000 a day — COVID-19 continues to be disproportionately fatal for those over 70 years. There were 22% deaths among those in the 70-80 years in the second wave compared to 19% in the first wave, and 9.8% deaths in those above 80 compared to 7.8% previously.
There is no evidence of any change in patterns of death in the younger age groups of 30-70 years, with about 70% deaths during both waves falling in this age bracket. However, for the mortality comparison, a far smaller sample — 24,814 — was used in the second wave compared with the 83,189 in the first wave.
Secretary, Health Ministry, Rajesh Bhushan, said the severity of the second wave meant that efforts were on to mitigate it and save lives, and only in the days ahead, with the benefit of hindsight, would it be possible to discern how India was attacked by a severe second wave.
There are 146 districts reporting a test positivity of over 15%, and these are the places were the hospital facilities are most taxed. There are 274 districts where case positivity is between 5% and 15%, and 308 districts where it is less than 5%.
India’s case fatality rate, Mr. Bhushan said, is at 1.17% and on decreasing trend from March 22, when it was 1.37%.