Here are the top 10 points in this big story:
The latest state to promise free vaccine is Madhya Pradesh. Amid the growing controversy, Chief Minister Shivraj Singh Chouhan tweeted: "My countrymen, we have taken many effective steps to protect the public from #COVID19. Today it is completely controlled. The preparation of Corona vaccine is going on fast in India, as soon as the vaccine is ready, it will be made available to every citizen of Madhya Pradesh for free."
Earlier, Tamil Nadu Chief Minister E Palaniswami, whose state is due to have assembly elections next year, said, "Once COVID-19 vaccine is ready, it will be provided to all people of the state free of cost".
Tamil Nadu's opposition DMK, which is trying to get back to power, said it would be the one to implement Mr Palaniswami's promise. Party spokesman A Saravanan said, "We would win elections and it will be the DMK government that would give free COVID vaccine in Tamil Nadu next year".
This morning, Union Minister Nirmala Sitharaman, who unveiled the BJP manifesto in Bihar, said: "As soon as a COVID-19 vaccine is available for production at a mass scale, every person in Bihar will get free vaccination". It was the "first promise" mentioned in the manifesto, the minister said.
The Congress was among the first to protest, with Rahul Gandhi, Shashi Tharoor and other leaders tweeting on the issue. "GOI just announced India's Covid access strategy. Kindly refer to the state-wise election schedule to know when will you get it, along with a hoard of false promises," Mr Gandhi's post read.
Delhi Chief Minister Arvind Kejriwal's Aam Aadmi Party questioned if people who do not vote for BJP get the free vaccine. "What about non-BJP ruled states? Indians who didn't vote BJP will not get free Covid vaccine?" it said.
National Conference leader Omar Abdullah questioned why only Bihar should get free vaccines. "Will BJP be paying for these vaccines from the party treasury? If it's coming from the government treasury then how can Bihar get free vaccines while the rest of the country has to pay? There is so much wrong with this blatant populism that shamefully exploits COVID fears," he posted.
Late in the evening, former Union minister Harsimrat Kaur Badal, whose party, the Shiromani Akali Dal, quit the government and the NDA over the controversial farm laws last month, called the BJP move "ridiculous". "Free vaccine only in Bihar? It's ridiculous! Does the whole country not pay taxes or are they not equal citizens of India? It's the GoI's duty to vaccinate the entire country. Using this life saving vaccine as a tool for votes is totally unethical," Harsimrat Kaur Badal tweeted.
Top Bihar BJP leader Bhupinder Yadav said the vaccine would be available at a nominal cost - not free - but it would be up to states to bear the cost. "Your (the Congress's) attempt to twist Nirmala Sitharaman's statement reeks of desperation. All parties issue manifestos. Vaccines will be made available to all Indians at nominal costs. States can make it free. In Bihar, we will," he wrote.
Today Covaxin, the coronavirus vaccine being developed by Bharat Biotech in collaboration with the Indian Council of Medical Research, got clearance for the third phase of clinical trials. Dr Reddy's Laboratories Ltd and the Russian Direct Investment Fund have said they have received fresh approval for clinical trials of the Russian vaccine.