NEW YORK • Work to distribute the experimental Covid-19 vaccine developed by Pfizer and BioNTech is gearing up after the companies announced successful interim data on Monday, but it will not be coming to local pharmacies for the public any time soon.
The data showed that the vaccine is 90 per cent effective at preventing Covid-19, and the firms are awaiting data on safety, which could come later this month.
Pfizer and BioNTech need to get regulators to sign off on the shot before they can start shipping vaccines to those considered most in need by the United States government. Healthcare workers and people living in nursing homes will likely top that list.
But the vaccine's complex and super-cold storage needs are an obstacle for even the most sophisticated hospitals in the US and may impact when and where it is available in rural areas or poor countries where resources are tight.
The main issue is that the vaccine, which is based on a novel technology that uses synthetic mRNA to activate the immune system against the virus, needs to be kept at minus 70 deg C or below.
"The cold chain is going to be one of the most challenging aspects of delivery of this vaccination," said senior scholar Amesh Adalja from Johns Hopkins Centre for Health Security.
"This will be a challenge in all settings because hospitals, even in big cities, do not have storage facilities for a vaccine at that ultra-low temperature."
Indeed, one of the most prestigious US hospitals - the Mayo Clinic in Rochester, Minnesota - said it does not currently have that capability.
Dr Gregory Poland, a virologist and vaccine researcher at the clinic, said: "We're talking about a vaccine that needs storage at minus 70 or 80. That's a tremendous logistical issue not only in the US, but outside the Western world.
"We're a major medical centre and we don't have storage capacity like this. That will be true for everybody. This is a logistical obstacle."
Pfizer spokesman Kim Bencker said the firm is working closely with the US government and state officials on how to ship the vaccine from its distribution centres in the US, Germany and Belgium to around the world.
The detailed plan includes using dry ice to transport frozen vaccine vials by both air and land at their recommended temperatures for up to 10 days, she added.
State and local healthcare providers are responsible for storing and administering vaccines once they have been delivered.
They can be kept in an ultra-low temperature freezer for up to six months, or for five days at 2 deg C to 8 deg C - refrigeration commonly available at hospitals, Ms Bencker said. The Pfizer storage units can also be refilled with ice for up to 15 days, she added.
But shots will spoil in around five days at normal refrigeration temperatures of slightly above freezing. BioNTech chief executive Ugur Sahin said the firms are analysing if they can extend that for two weeks.
Meanwhile, the vaccine developed by Moderna Therapeutics, which is based on similar technology, does not need to be stored at such a low temperature. Other vaccines, including those from Johnson & Johnson and Novavax, can be stored at 2-8 deg C, the temperature of a regular refrigerator.
Scientists, public health officials and investors have welcomed the first successful interim data from Pfizer as a watershed moment that could help turn the tide of the pandemic if the full trial results pan out.
Emerging infectious diseases professor Peter Horby from the University of Oxford said: "This news made me smile from ear to ear. It is a relief to see such positive results on this vaccine and bodes well for Covid-19 vaccines in general."
However, experts said they wanted to see the full trial data. There are still many questions, such as how effective the vaccine is by ethnicity or age and how long immunity may last.
"But the bottom line is, as a vaccine, it's more than 90 per cent effective, which is extraordinary," top US infectious diseases expert Anthony Fauci told CNN.
Pfizer expects to seek US emergency use authorisation for people aged 16 to 85. To do so, it will need two months of follow-up safety data to assure that no side effects crop up. That is expected to be available next week.
Experts said the cold storage needs could impede Pfizer's ability to reach rural healthcare systems and nursing homes, or less wealthy countries, which may not have the funds for the refrigeration units.
Ms Claire Hannan, executive director of the Association of Immunisation Managers, a lobby group for local public health officials who handle vaccines, said: "If Pfizer's is the only vaccine to be authorised in the next few months, we do worry about equity when it comes to spreading it to rural areas."
Some states have already said they have a shortage of ultra-cold freezers, according to public documents that states filed with the US Centres for Disease Control and Prevention.
Without the extra equipment, doctors will have a dilemma: Store vaccines in standard refrigerators and deploy all 975 doses in each Pfizer vaccine container in less than five days, or restock them with dry ice and open them only twice a day to extend the vaccines' life span, said Ms Hannan.
Meanwhile, the World Health Organisation warned that there is a funding gap of US$4.5 billion (S$6.1 billion) that could slow access to tests, medicines and vaccines in low-and middle-income countries.