India may approve some coronavirus vaccines over the next few weeks, the country's top health official said on Tuesday.    

"There are multiple vaccine candidates in different stages of development and some of them may get licensed in the next few weeks," Health Secretary Rajesh Bhushan told a press briefing in New Delhi.

Over the weekend, pharma giant Pfizer sought emergency use authorization in India for its coronavirus vaccine developed in partnership with Germany's BioNTech. A couple of other companies have also submitted applications for emergency use approval for their vaccines.

Indian Prime Minister Narendra Modi has repeatedly emphasized the importance of a vaccine to rein in COVID-19. 

Where are we now in terms of vaccine development?

If and when authorities grant emergency use authorization, it would mark a significant step in India's efforts to put an end to the acute health crisis that has overwhelmed the South Asian nation's healthcare infrastructure and triggered the sharpest economic contraction in decades.

Vaccines usually require years of research and testing before reaching the clinic. They have to be proved safe and effective in animal studies, then in small trials in healthy volunteers, followed by large trials in representative groups of people, including the elderly, the sick and the young. 

The aim of a vaccine is to prevent a disease by working with the body's natural immune response. When a vaccinated person is exposed to the virus, the immune system recognizes the pathogen and prevents the person from getting infected or sick.

Recent publication of clinical data showed that the BioNTech-Pfizer vaccine was more than 90% effective at preventing illness in large-scale human trials.

The Drugs Controller General of India (DCGI) may give emergency approval if it is satisfied by the results of the trials conducted outside India, Indian broadcaster NDTV reported. The regulator has "discretionary power to waive localized clinical trials for a vaccine," officials said. 

What other vaccine candidates are under consideration?

At present, three prominent vaccine candidates are being tested in India, only one of which — Covishield — had reached Phase-3 trials. Covishield, developed by Oxford University and AstraZeneca, is being tested in India by the Pune-based Serum Institute, which has committed to producing millions of doses for India and other low- and middle-income countries, should the vaccine candidate prove successful and be cleared by regulators.

The other two candidates are being tested by the firms Zydus Cadilla and Bharat Biotech.

Bharat Biotech also filed an application on Monday seeking emergency use authorization for its COVID-19 vaccine, while Serum Institute sought fast-track approval for AstraZeneca-Oxford's coronavirus shots.

Serum Institute CEO Adar Poonawalla said approval for distribution of the AstraZeneca-Oxford vaccine — of which the company is already making 50 to 60 million doses a month — "will save countless lives."

Poonawalla said last month the doses would be sold to the Indian government at around 250 rupees ($3, €2.5). "As promised, before the end of 2020, @SerumInstIndia has applied for emergency use authorisation for the first made-in-India vaccine, COVISHIELD," Poonawalla tweeted.

But AstraZeneca's vaccine is facing queries from scientists over the robustness of some of its trial data, which showed a 1.5 dose regimen delivered more than 90% efficacy and a full two-dose regimen just 62%, both administered over two stages.

What logistical issues are involved in the vaccine distribution?

BioNTech-Pfizer's vaccine is based on a new technology that uses genetic material in the form of mRNA (messenger ribonucleic acid) and requires ultra-low temperatures for transport and storage. It needs to be kept at minus 70 degrees Celsius (minus 94 degrees Fahrenheit).

Experts in India have raised concern about the logistics involved as most vaccines in the country are stored between 2 and 8 degrees Celsius.

AstraZeneca's vaccine, meanwhile, uses a more established technology and will be easier to transport and store, as it can be stored at the temperature of a normal refrigerator.

The delivery of the vaccines to the people who need them will ultimately depend on the supply chains, cold chain equipment, disease surveillance efforts, comprehensive data recording and trained health care workers.

For now, the government hopes to rope in its nearly 240,000-strong vaccinators from its Universal Immunisation Programme (UIP) to manage the logistics of administering COVID vaccines.

The UIP, managed by the Health Ministry, covers 25 million children every year, inoculating them against a range of diseases including measles, polio, and tuberculosis.

"The biggest challenge will be how the program will be rolled out and it has to be in batches. This is an intramuscular injection that requires two jabs within 3 to 4 weeks. It has to be done by trained personnel and that is why a special task force for vaccination is a good idea," K Srinath Reddy, president of the Public Health Foundation of India, told DW.

What other difficulties are expected?

Procuring enough shots for India's 1.3 billion people and distributing them widely and equitably in a short time span could also pose a challenge.

Moreover, global demand for COVID vaccines is likely to outstrip supply until at least 2022, and rich countries have already reserved billions of doses of the leading vaccine candidates through direct bilateral deals with pharmaceutical companies.

Who will likely receive the first shots?

To reduce the number of people dying from COVID-19, those most at risk of exposure or severe infection will need to be immunized first, say experts. This includes health care and police personnel, older adults and people with other illnesses.

The government has identified 300 million people, including health care workers, policemen, and citizens above the age of 50, who would be administered a vaccine on a priority basis, Health Secretary Bhushan said.

"Every single Indian who needs to be vaccinated, will be vaccinated," Bhushan said, adding that the government expected the vaccination process to take over a year to complete.

How important is India when it comes to ensuring adequate global vaccine supply?

Indian drug companies are big manufacturers of vaccines distributed worldwide, particularly those for low- and middle-income countries.

The Serum Institute of India (SII) has an agreement to manufacture one billion doses of the Oxford-AstraZeneca vaccine if it is approved for use.

In April, Serum's CEO Poonawalla told DW that the company's decision to mass produce the AstraZeneca candidate before the vaccine was proven effective was made solely to have a head start on manufacturing and to have enough doses available.

If the vaccine worked, SII and the Indian government committed to reserve half the company's stock of it for India, and to supply half to low-income nations through GAVI vaccine alliance, a sponsor of immunizations for low-income nations.

"If the trials are successful, we will make the product available in as many countries as possible, including India. When a vaccine is developed, we plan to sell it for around €12 ($13) per dose," said Poonawalla.

Additional reporting by Murali Krishnan from New Delhi.