Covid-19 vaccine expiry dates may be extended amid growing frustrations that countries in Africa are being forced to dump jabs because they have a short shelf-life.
Last month, Malawi incinerated 20,000 expired doses of the AstraZeneca/Oxford University vaccine. The manufacturer said they would be safe to use for another three months, but ministers were concerned that using them would hit already shaky vaccine confidence.
Meanwhile, the Democratic Republic of Congo has sent 1.3 million unwanted doses to countries including Togo and Senegal because of fears they would not be able to administer them before they expired, and South Sudan sent 72,000 shots to Kenya.
Both the AstraZeneca and Pfizer jabs have shelf lives of six months, although once the Pfizer vaccine is taken out of its deep-freeze storage conditions it must be used within a month. Sinopharm's vaccine is an exception, with a shelf-life of two years in refrigerated temperatures.
Vaccine expiry dates and shelf-life are determined by the manufacturer and approved by regulatory authorities based on "stability data". Regulators have to give the go-ahead for any change to expiry dates.
Gavi, the Vaccine Alliance, one of the co-founders of the Covax vaccine distribution scheme, has previously suggested that the expiry dates for the Covid-19 vaccines are "cautious". Many other vaccines are usable for up to three years.
A spokesperson for Gavi told Britain's Daily Telegraph: "It's worth noting that expiry dates could be extended as stability data for longer periods of time become available for subsequent vaccine batches."
Because of the rapid development of Covid vaccines, the World Health Organisation (WHO) issued initial emergency use authorisation for the AstraZeneca jab when only six months worth of data was available.
Shelf-life of a vaccine is a reflection of how long the vaccine retains its potency and stability at a given storage temperature, and therefore its effectiveness, rather than safety.
The Serum Institute of India, which manufactures the bulk of the AstraZeneca shots distributed in Africa, is working with WHO to provide all the data needed for the organisation to give the go-ahead for expiry dates to be lengthened.
Chief executive Adar Poonawalla said Serum is looking for a nine-month expiry date, but he was incredulous that this would ever be needed, given the demand.
"The minute we deliver vaccines they usually just administer them," he told the Telegraph. "In fact, it is absolutely criminal if vaccine doses are wasted and are not used."
However, leading figures in Africa's vaccine roll-out said that countries were being given the vaccines without enough time to complete distribution before the initial expiry dates kicked in.
Dr Ayoade Alakija, co-chair of the Africa Union's Vaccine Delivery Alliance, told the Telegraph that the issues were another sign that Africa was "always last in line, the afterthought".
"We were sent the vaccines that weren't first off the production line; late deliveries [meant a] limited time to distribute [them]," she said.
"Some of the vaccines were rushed into countries with next to no preparation and little dialogue with national authorities. This in countries with already weakened health systems and limited capacity."
In total, the WHO Africa region has redistributed more than 925,000 doses because countries were unable to administer them.
Vaccine campaigns have been slow partly due to vaccine hesitancy – accentuated after much of Europe temporarily suspended AstraZeneca rollout due to concerns about very rare blood clots – and partly because of bottlenecks in distribution and a lack of funding for rollout.
"Expired vaccines that are 'okay' don't help vaccine confidence at all," said Dr Alakjia. "It really has been perceived as giving leftovers to the needy."
But Africa is not the only continent struggling with tight timetables.
In its weekly epidemiological report on Wednesday, the WHO said there had been "challenges" in a number of low and middle income countries, pointing out that many countries received vaccines that were already well into their six months of usability.
"Where there was slow roll-out of vaccines, it was challenging to use them in a timely manner," the report added.
There have been issues in higher income countries, too. Last week Canadian regulators approved extending the shelf life of two batches of Oxford-AstraZeneca shots that had been due to expire on Monday.
Amanda Harvey-Dehaye, task force leader at Médecins Sans Frontières for the WHO's Access to Covid Tools Accelerator, told the Financial Times there needed to be a more transparent discussion about vaccine expiry.
"Given the risk of thousands of doses being destroyed, it's a shame we have so little visibility over stability tests run by manufacturers – and the subsequent extensions to shelf-life," she said. "The current expiry dates add real pressure to vaccination campaigns that can already be heavily challenged."