Shot in the dark

India's precautionary dose rollout indicates that the world is reluctant to move beyond vaccines in the fight against COVID-19. How practical and viable is this booster-shot strategy?

- TARAN DEOL

0N APRIL 10, just as several states recorded fresh flareups of novel coronavirus infection (COVID-19) following weeks of sharp decline in new cases, India extended access to a third dose of COVID-19 vaccine to all adults who have received the second shot nine months earlier. The vaccine, dubbed a precautionary dose, had been available to those above 60 years and healthcare workers since January 10, this year. With the announcement, India joins some 100 countries that have since July 2021 begun rolling out booster shots.

While India offers the vaccine used for primary shots as the precautionary dose, all other countries have allowed mix-and-match of vaccines based on data that shows this is safe and effective. Some also offer repeated booster shots. Israel rolled out a second booster dose in January, while the US has approved the same for those above 50.

Does this mean, the pandemic now enters the phase where frequent boosters will be needed? If yes, what is the magic number and how frequently should it be given? These are the questions health officials worldwide are scrambling to answer.

The World Health Organization (WHO) had until January this year only urged for broader global access to primary and booster vaccine shots, but on March 8 it intensified its stance to “strongly support" the same. WHO's change instance came in the backdrop of emerging variants, breakthrough infections and data showing a steady decline of immunity among vaccinated individuals. A study published in New England Journal of Medicine in February 2022 finds that protection after two shots of Pfizer Inc's vaccine waned considerably after six months. Another study published in