NEW DELHI — India has administered more than a billion COVID jabs since it started its vaccination drive in January this year. It achieved this milestone in 278 days — the first vaccine was given on Jan. 16.

It has fully vaccinated about 30% (291 million) of the eligible population and 707 million have had the first dose. India aims to fully vaccinate about a billion people by the end of 2021 but experts say the drive needs to pick up pace further to meet the target.

This milestone makes India the second country to reach the one billion mark — China crossed it in June.

To celebrate the record, the government plans announcements over loudspeakers on trains, planes, and ships. Union Health Minister Mansukh Mandaviya will launch a song by singer Kailash Kher.

The largest national flag, weighing around 1,400 kg, will also be raised at the Red Fort, news agency PTI reported.

Reaching the one billion mark in 278 days means that India, on an average, administered 3.6 million doses per day. However, the number of doses actually administered each day since January was not consistent, and varied widely.

So far, the country has reported more than 34 million COVID cases, second only to the US, and more than 452,000 deaths — behind the US and Brazil.

The World Health Organization has congratulated Indian Prime Minister Narendra Modi after the country achieved over a billion COVID-19 vaccinations milestone Thursday. WHO Director-General Tedros Adhanom Ghebreyesus posted a tweet to congratulate PM Modi.

Modi, who visited the Ram Manohar Lohia Hospital in Delhi to mark the milestone, congratulated the country and called it "the triumph of Indian science, enterprise and collective spirit of 130 crore Indians,"

The five states that have administered the highest number of doses are Uttar Pradesh, followed by Maharashtra, West Bengal, Gujarat, and Madhya Pradesh.

Dr. V.K. Paul, NITI Aayog member and chief of the government's vaccine panel, said it was remarkable to reach the one billion dose mark in just over nine months since the vaccination program started in India.

Dr. Paul, stressing the need for consistency, pointed out that even though the first dose has been given to over 75 percent of adults, 25 percent remain unvaccinated.

WHO's Regional Director, South-East Asia, Dr. Poonam Khetrapal Singh said that this "extraordinary feat" was not possible in a short span without "strong political leadership, inter-sectoral convergence, dedicated efforts of the entire health & frontline workforce."

Experts estimate that the country needs to give more than 12 million doses a day to fully vaccinate all eligible adults by the end of 2021.

On Sept. 17, India administered more than 20 million doses in a day in a record-breaking effort to mark Prime Minister Narendra Modi's 71st birthday.

In October, India administered an average of 5.3 million doses per day. From Sept. 19 to Oct. 18, the average daily doses given slightly improved to six million.

India had a slow start when vaccinations were opened for some 960 million eligible people. Logistical problems and supply bottlenecks, vaccine hesitancy and a debilitating second wave of COVID-19 during this period made the rollout harder.

From a sluggish start, India massively ramped up its vaccination drive, with more than 61,000 public and private health facilities offering the jab.

The country has also started delivering vaccines by drone to far-flung villages in north-east India's mountainous regions.

Drones will also be used to ferry doses to the eastern archipelago of Andamans and Nicobar where "transportation by boat" was taking a long time.

The government is using drones which can carry a payload of 4.5kg or a maximum of 900 doses and fly at least 70km (43 miles) to ferry doses.

While the vaccination drive has gained momentum, experts worry about a gender gap - government data shows 6% fewer women are getting vaccinated.

This is especially true in rural India where women have limited access to the Internet and are hesitant or scared to take the vaccine.

Although a higher number of doses are being administered daily in rural areas, the share of population being vaccinated in urban areas is still greater.

India is using three vaccines — the Oxford-AstraZeneca jab, known locally as Covishield; Covaxin by Indian firm Bharat Biotech; and Russian-made Sputnik V.

The three-dose ZyCoV-D vaccine prevented symptomatic disease in 66% of those vaccinated, according to an interim study quoted by the vaccine maker Cadila Healthcare. The ZyCoV-D vaccine is also the world's first DNA vaccine against COVID-19.

The government has also authorized Indian pharma company Cipla to import Moderna's vaccine, which has shown nearly 95% efficacy against COVID-19. But it's not clear yet how many doses will be made available to India. — Agencies