For the past two days, Sanjay Kumar has been trying to get himself and his ageing mother vaccinated against coronavirus in the northern Indian state of Uttar Pradesh.
"I called up three private hospitals in my neighbourhood and all of them said they had run out of doses," says Dr Kumar, a social scientist, who lives in Ghaziabad, on the outskirts of Delhi.
One of them is a 50-bed neighbourhood hospital. "We have zero stock of vaccines and are not taking bookings because people come for jabs and get into fights (when we tell them we have no stocks)," a front office worker said. At another hospital where Dr Kumar unsuccessfully sought a booking, officials said they had run out of doses on Wednesday evening. "We have no other option but to turn people away," an employee said.
As India grapples with a deadly second wave of Covid-19 infections - with an average of more than 90,000 cases daily from 1 April - its vaccination drive appears to be struggling. Half a dozen states are reporting a shortage of doses even as the federal government insists that there's enough in stock.
In the western state of Maharashtra, which is reporting more than half of India's new infections, the inoculation programme appears to be grinding to a halt. The local government says its current stock of 1.5 million doses will last only for three days. Vaccination centres have been shut in the state capital, Mumbai, and parts of Kolhapur, Sangli and Satara districts. "If the vaccines don't come in three days, we will be forced to stop the drive," state Health Minister Rajesh Tope told reporters.
Federal Health Minister Harsh Vardhan says the "allegations" of vaccine scarcity are "utterly baseless" - more than 40 million doses are "in stock or nearing delivery", he claims. He blames states for trying to "divert attention from their poor vaccination efforts by just continuously shifting the goalposts". Mr Vardhan believes the states which are complaining of shortages have not even fully vaccinated their frontline workers.
That may not be entirely true. Vaccine shortages seem to be a reality in some states who have managed to vaccinate quickly, according to Oommen C Kurian of the Observer Research Foundation, a Delhi-based think tank. He told me that the shortage might be triggered by a "mismatch between the claimed production capacity of Indian vaccine makers and the actual produced doses over the last four months or so".
India's vaccination drive, the world's biggest, began on 16 January, and aims to cover 250 million people by July. Initially limited to healthcare workers and frontline staff, it has been since extended in stages to people above 60; those between 45 and 59 who have other illnesses; and those above 45.
More than 90 million doses of two approved vaccines - one developed by AstraZeneca with Oxford University (Covishield) and one by Indian firm Bharat BioTech (Covaxin) - have been given so far. An average of three million jabs are being administered daily. Also, India has so far shipped 64 million doses of vaccines to 85 countries. Some are in form of "gifts", others in line with commercial agreements signed between the vaccine makers and the recipient nations, and the rest under the Covax scheme, which is led by the World Health Organisation (WHO).
When it comes to vaccine manufacture, India is a powerhouse. It runs a massive immunisation programme, makes 60% of the world's vaccines and is home to half a dozen major manufacturers, including the Serum Institute of India - the largest in the world. But a large-scale adult vaccination programme against a virulent pathogen like SARS-Cov2, the virus that causes Covid-19, is posing unprecedented challenges.
For one, experts say the vaccination drive needs to pick up a lot more pace in order to meet its target. It is not clear whether the country has enough vaccines and state capacity to expand the drive.
The key question, as many have been speculating, is whether India has enough stock of doses to speed up the drive and expand coverage to include the young. Some are wondering whether India did the right thing by sending millions of doses abroad as part of its much hyped "vaccine diplomacy".
Serum Institute of India, which makes the Oxford-AstraZeneca vaccine, known locally as Covishield, has provided some clues. This week, it said its production capacity was "very stressed". Adar Poonawalla, the head of the firm, said in an interview on Indian television that "we are still short of being able to supply to every Indian."
Serum says it has been providing 65-70 million doses every month to India, and exported a total of nearly an equal amount of doses since it began production early this year.
In January the firm told the BBC that it was aiming to boost production to 100 million doses a month. Now it says it would not be able to meet the target before the end of June because of time taken to repair damages from a fire at its facilities in the western city of Pune in January. Then Mr Poonawalla had said there would be no impact on the production of Covishield, "due to multiple production buildings that I had kept in reserve to deal with such contingencies".
The firm says a squeeze on finances is also hampering the drive to ramp up production. Mr Poonawala is seeking $400m (£290m) in government assistance or bank finance to invest in expanding capacity. Serum is selling a dose of the vaccine at $2 to India's government and "this rate is not enough to sustain further expansion," he says.
"This was not budget or planned initially because we were supposed to export [more] and get the funding from exporting countries. Now that is not happening and we have to find other innovative ways to build our capacity, so we can support our nation in light of the surge in cases," Mr Poonawala told NDTV.
Clearly, India's vaccine "shortage" will have a worldwide impact.
Last month India placed a temporary hold on all exports of the Oxford-AstraZeneca coronavirus vaccine. Serum says it shipped 30 million doses to Covax in January and February - half of its capacity - and now there's a shortfall of "30-40 million [export] doses".
"We have told them the need [for doses] is India is so severe that we need to prioritise Indian needs over that of exports," Mr Poonawala told CNBC-TV18. He also told Business Standard newspaper that Astra Zeneca had sent his firm a "legal notice (for delays in supplying the vaccine) and the Indian government is also aware of that".
Experts say the vaccine shortages in parts of India could be because of supply bottlenecks. Vaccine makers had also possibly "oversold" their capacities while taking orders from all over the world. "As the cases rise and vaccine hesitancy falls, the demand for doses will increase. We have to plan better," says a senior official, who preferred to remain unnamed.
At the moment, India doesn't have too many options. A new vaccine - possibly Sputnik V - is expected to be approved by June. Covovax, another coronavirus vaccine being developed by Serum Institute in partnership with American vaccine developer Novavax, is not expected to be available before September.
So India has to prioritise jabs. There's no other way to bring down the number of people dying of Covid-19 than to speedily provide shots to more than 120 million of India's elderly. This needs to be done in the next few weeks, with the help of local governments, civil society, including religious leaders and backed by focused communication campaigns, says Mr Kurien.