Last week, the Food and Drug Administration approved the emergency use of covid-19 vaccine from the American biotechnology company Moderna. The week before, the FDA approved vaccination with a substance from the American pharmaceutical company Pfizer and the German company BioNTech.
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Both of these two-dose vaccines are highly effective, according to the office. However, there is also evidence to suggest that, for example, only one dose of a product from Moderna can stop the spread of the virus, NBC News wrote, referring to information from the FDA. A document published on the FDA website shows that asymptomatic infection was reduced by 63 percent after the first injection.
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Another Food and Drug Administration document from last week also mentions an analysis of participants who received only one dose of Moderna or placebo – the effectiveness of one dose of vaccine (half as planned) in this limited sample was as high as 80-90 percent. However, the number of participants in the resulting clinical study was limited and further trials would be needed.
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Given the limited supply of vaccines and the hundreds of millions of people waiting to be vaccinated, epidemiologists and other experts have something to think about.
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“This question is really difficult – both moral and scientific,” said epidemiologist Barry Bloom of Harvard University, according to the American radio station WBUR-FM.
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“If the second dose of the vaccine was redundant and we knew it would not extend the term of protection, the principle should really be to protect as many people as possible and save as many lives as possible,” he said quite clearly.
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Immunologist Hořejší: It makes sense
People are even calculating the difference in vaccination coverage and how effective it would be. Giving Pfizer and Modern only one dose as long as resources are severely limited, as it may be better to have two people protected at 90 percent than just one, even at 95-99 percent?
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Because the hypothesis states:
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- Example (100 doses of vaccine, 100 people, 1 dose = 90% immunity, 2 doses = 95% immunity)
- A: you give 2 doses to 50 people = average immunity of the population 47.5%
- B: you give 1 dose to 100 people = average immunity of the population 90%
Here’s a good explanatory video.
Example (100 doses of vaccine, 100 people, 1 dose = 90% immunity, 2 doses = 95% immunity)
A: you give 2 doses to 50 people = average immunity of the population 47.5%
B: you give 1 dose to 100 people = average immunity of the population 90%https://t.co/phoCg8HMf6– Michal Sirový (@sssirda) December 20, 2020
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And what about the expert if a single dose would actually have a proven 90% effectiveness? “Yes, that makes sense. In addition, there is no need for those -80 degrees for storage, ”commented Václav Hořejší from the Institute of Molecular Genetics of the Academy of Sciences of the Czech Republic for Novinky.
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In any case, the correct answer depends on scientific knowledge, which is still far from complete in this area and requires further verification.
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An even better chance at Moderna?
First, sufficient protection with a single dose of the vaccine has not been definitively demonstrated with Pfizer. Researchers can deduce from the data from the studies that Pfizer’s vaccine will provide protective antibodies to only about half of the people who receive a single dose.
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Christopher Gill, an infectious disease and vaccine development specialist at Boston University, argues that a single injection of Pfizer may be more effective. Looking at the data from the shorter time between when the first dose was supposed to work and before the second, the Gill for WBUR-FM claims that Pfizer / BioNTech can be as effective as 80 or 90 percent – with just one dose.
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Approximately 2,000 participants in Moderna’s phase three clinical study received only one injection of placebo or vaccine. In this population, the effectiveness of a single dose of vaccine was about 80 to 90 percent, as already mentioned. “However, the efficacy observed after dose 1 and before dose 2 cannot support the conclusion about the efficacy of a single dose of vaccine because the number of participants and the duration of observation are limited,” the FDA warns, adding that more comparative studies are needed.
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Thus, the first doses of some vaccines could theoretically be as effective as up to 90 percent after 14 days. According to some experts, this could work at least in the future, so that at least the first dose should be given to high-risk cases as soon as possible. The latter may be given later if the effectiveness of the first dose decreases or the supply improves. So far, we have no idea how long a single dose would work – and whether the age or health status of the vaccinated would not play a role. However, as a consideration for the future, it is interesting.
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However, most vaccines still require two doses – in addition to the Johnson & Johnson single-dose substance.
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