India began administering booster doses of COVID-19 vaccine to frontline workers and vulnerable elderly people on Monday, with the fast-spreading Omicron variant fuelling an almost eight-fold rise in daily infections since the start of the year.
India reported 179,723 new cases on Monday, most of them in the country's biggest cities - Delhi, Mumbai and Kolkata - where Omicron has overtaken Delta as the most prevalent strain of the virus.
There were 146 deaths reported on Monday, bringing the toll to 483,936 since the pandemic first struck India in early 2020. Only the United States and Brazil have recorded more deaths.
In recent days, hundreds of healthcare and frontline workers, including police, have contracted the virus, and there were media reports that hundreds of parliamentary staff have also tested positive ahead of a budget session on February 1.
Facing this rising third wave of infections, the government sent booster reminders to more than 10 million people who took their second dose of the Covaxin or Covishield shot nine months ago.
Unlike many countries, India is not mixing and matching vaccines.
Only healthcare personnel, frontline workers and people above 60 years suffering from other health conditions are eligible for what the government calls a "precaution dose".
"The government is committed to provide additional security cover to healthcare and frontline workers on priority," Health Minister Mansukh Mandaviya wrote on Twitter.
Despite the rise in infections, five states including the most populous Uttar Pradesh will hold elections starting February 10, though authorities have barred political party rallies until at least the middle of this month.
Tasked with protecting India's near 1.4 billion people from the virus, the government has administered 1.5 billion vaccine doses in total. About 67 per cent of the country's 939 million adults have been double vaccinated.
India's overall COVID-19 testing has remained around 1.5 million a day, well below the capacity of more than 2 million.
Since the pandemic began, India has recorded 35.7 million cases of COVID-19, the highest in the world after the United States.
Government officials have privately said they are working under the assumption that daily infections will surpass the record of more than 414,000 set in May, based on what has happened in countries like the United States, where daily cases have risen past 1 million.