Updated: November 11, 2020 7:14:52 am
Pfizer and German partner BioNTech SE are the first drug manufacturers to show successful data from a large-scale clinical trial of a coronavirus vaccine.
While Pfizer and BioNTech await sufficient safety data In late November, to seek emergency approval for its Covid-19 vaccine in the US, two obvious limiting factors make rapid scaling up and deployment difficult: the task of ensuring that each recipient receives two injections exactly three weeks apart. difference and organize cryogenic logistics distribution network.
In addition to this, four other possible limiting factors emerge from preliminary information released yesterday from its phase 3 human trials of the vaccine: Does it prevent infectivity? Analysts point to the possibility that it could prevent someone from contracting Covid-19 symptoms, but not from spreading it to others, and does it work well in high-risk groups like the elderly?
Most importantly: how long does the immunity it provides last? While more clarity about the vaccine would emerge as the final stage of the trial progresses, this question could take months, even years, to answer.
Global stock markets reacted strongly to interim data released by Pfizer on Monday: Out of 94 participants, the vaccine was “more than” 90 percent effective in preventing Covid-19 among those who had received two doses. However, the caveat here is that these injections will need to be kept in ultra-cold storage.
READ | Pfizer Covid-19 Vaccine Preview: After Talks With Regulators, India’s Cold Chain Is A Challenge
“Initially, our potential COVID-19 vaccine will need to be stored at -75 ° C ± 15 ° C,” a Pfizer spokesperson told The Indian Express. This means strengthening the capacity of existing freezers to hold millions of doses at temperatures between -90 ° C and -60 ° C, something for which, according to experts, no country is really prepared.
“These vaccines are going to be expensive and storing and delivering will be challenging,” said vaccine scientist and Christian Medical College professor Dr. Gagandeep Kang de Vellore.
“This is a specialty requirement, which very few pharmaceutical companies have in a small capacity,” said Sunil Nair, CEO of Snowman Logistics, which has been studying the possibility of upgrading its current cold chain capabilities in the country to levels cryogenic.
According to him, the general capacity of existing cold stores in India can store between 4 and 5 million doses of a vaccine. “The units (below zero) that we have heard about from pharmaceutical companies can store between 25,000 and 30,000 doses,” he added.
While Pfizer is known to make its own dry ice and to have ties to companies such as FedEx and UPS, which have the logistical capacity to supply ultra-low temperature drugs, this sophisticated supply network is largely restricted to developed markets. The availability of dry ice supplies and the logistical capacity to transport and maintain the vaccine at such temperatures could be a limiting factor in a place like India.
“Much of India’s cold chain capacity (for its universal immunization program) depended on the polio vaccine, which requires prolonged storage at -20 ° C and then 2 ° C to 8 ° C. (when distributed for vaccines). This requires -80 ° C, which uses two compressors instead of -20 ° C, which uses one, and the amount of electricity used to run them is also much higher. For a country like ours, where electricity is a problem, it will not be enough to increase the cooling capacity for a vaccine like this, ”said Dr. Kang.
Not surprisingly, while Pfizer has agreements with some governments in the west to supply limited doses of the vaccine, most Asian and African countries are more inclined to handle a vaccine that can be stored closer to room temperature.
In fact, the Indian government’s thinking so far on increasing cold chain capacity does not prioritize vaccines that require sub-zero storage temperatures.
“The increased capacities would not have freezing temperatures, because we still believe that eventually we will not require such vaccines in large quantities. We may not need them at all, ”said a senior government official who was familiar with the center’s evolving strategy to vaccinate priority groups by July 2021.
The data presented from the trials – in the United States, Germany, Brazil, Argentina, South Africa and Turkey – is not a final analysis, as it is based on only the first 94 volunteers, some experts caution. The vaccine effectiveness metric may be subject to change when the full results are analyzed, they believe.
“First of all, these are provisional data … from the study of 44,000 (participants) conducted by Pfizer in the United States. We know from previous experiences with vaccines that vaccine efficacy can vary greatly from country to country, population to population, and the big surprise comes when you take people from high-income countries and compare them to income countries. medium to low, ”Massachusetts said. vaccine expert Dr. Davinder Gill. “It was 90 percent effective in the United States, but what was it in Brazil or South Africa? I think that until it comes out, the question of how effective this vaccine is in multiple populations, different demographics, ethnic groups, and genders will remain. “
The two companies say they will be able to supply 50 million doses by the end of this year and about 1.3 billion by the end of 2021. Each person needs two doses. Which translates to 25 million people in the remaining days of this year and 650 million people next year.
The vaccine uses a completely experimental mRNA method, which consists of injecting part of the genetic code of the virus to sensitize the immune system. Previous trials have shown that the vaccine trains the body to produce both antibodies, as well as T cells, to fight the coronavirus.
“This (mRNA) is a new technology and these vaccines will be manufactured very carefully to ensure stability, because one of the big problems with RNA vaccines is stability,” Dr. Kang said.
“We now have a proof of principle that the vaccine, which is based on the expression of the pico protein (the pointed outer shell of the SARS-CoV-2 virus), works. That means other peak protein-based vaccines are even more likely to work as well, ”he said. “My thinking is that we should wait until we have a peak protein vaccine that matches our ability to deliver, which would make things at least a little less complicated … rather than looking for a successful vaccine and trying to fix our management system so that everyone can get it, ”he added.
Despite all the limitations, the big advantage of the mRNA approach, which has never before been shown to work in humans, is that the data collected from large-scale trials means that companies can perform minor mRNA sequence revisions. quickly and easily. thus modifying the proteins to which the body develops immunity. This means that if new strains of the virus emerged, changes could be made to the vaccine quickly to accommodate the viral mutations.
While the vaccine, labeled BNT162b2, has been tested in more than 43,500 people in six countries and no safety concerns have been raised, the latest details released by the developers leave a question mark as to whether the vaccine prevents infectivity. of the need for clarity. on its long-term efficacy and effectiveness in key vulnerable groups, such as the elderly. The Oxford-AstraZeneca vaccine is already known to stimulate a good immune response in the elderly.
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