India has dramatically increased Covid-19 vaccination rates in its vast rural hinterland, where around 65% of the country's nearly 1.4 billion people live.

However, supply constraints remain for the world's largest maker of vaccines and experts say it is unlikely India will reach its target of vaccinating all adults by the end of the year.

India began offering jabs for all adults in May, but the campaign faltered in villages due to vaccine hesitancy and misinformation.

That started changing in mid-July, and of the nearly 120 million shots administered in the past three weeks, around 70% were in India's villages - up from around half in the initial weeks of May.

Although the increased vaccine acceptance in rural areas is promising, the pandemic is far from done in India: After weeks of steady decline, the 46,000 new infections reported on Saturday was its highest in almost two months.

Only about 11% of India's vast population is fully vaccinated, while half of all adults and about 35% of the total population have received at least one shot. This has left large swathes of people still susceptible to the virus.

Several nations, including the US and Israel, are offering or plan to offer booster shots to people, deepening global vaccine inequity.

India was expected to be a pivotal producer of shots to immunise the world but stopped exports after an explosion of infections.

And while India had expected to get 1.35 billion shots in the final five months of 2021 to resolve its supply constraints, the question of whether Indian vaccine makers can scale up production to meet the country's needs will have global implications.

"Currently in India, there is more demand than available supply... the supply of vaccines currently in use is lower than the projections made a few months ago. So both of these situations are putting constraints on availability of vaccines in the country," said Dr Chandrakant Lahariya, a vaccine policy expert.

India is no stranger to mass immunisations, but this is the first time that shots are being given at this scale, and to adults.

Officials have blended strategies that were successful in the past with newer, more localised innovations.

Kamalawati, 65, a retired government accountant who goes by only her first name, lined up for a shot at Nizampur, a village outside New Delhi. She said people initially were concerned there would be harmful side-effects but "people are not scared anymore".

What has worked for her village and others is a contest in which the local government awards a trophy to the village with the most vaccinated people and a plaque declaring the village the winner. Stickers are also pasted on homes where people are fully vaccinated to encourage neighbours to do the same.

District administrator Saumya Sharma said the campaign relies on the sense of community and pride residents have in their village.

"That this is our village. And we are going to make it number one," she said.

Public health experts say the uptick in rural vaccinations is important because healthcare systems in villages are fragile.

The deadly surge of infections that overwhelmed hospitals earlier this year ripped through rural India and thousands died.

Moreover, migrants from villages move to cities for work and until everyone is vaccinated, outbreaks and even the possibility of a dangerous new variant cannot be discounted.