New research suggests that the covid-19 vaccine developed by AstraZeneca and Oxford University will not only offer protection against the symptoms of viral disease, but will also reduce a person’s risk of transmitting the virus to others. Although scientists have been optimistic that this and other covid-19 vaccines will reduce the risk of transmission, new data are some of the first direct evidence to support this assumption.
Researchers at Oxford University in the United Kingdom released this week’s data in a prepress paper for the Lancet. Prepresses are preliminary research papers that have not yet gone through the formal peer review process, so conclusions should be viewed with more caution. However, the conclusions of his study (an analysis of long-term data from clinical trials of the vaccine in the UK and Brazil) appear to be encouraging.
On the one hand, the results suggest that even a single dose of the Oxford / AstraZeneca vaccine may be 76% effective in preventing coronavirus disease 21 days after receiving it (it is believed that 21 days will elapse before the immune system grows an effective response against the virus). It is important to note that efficacy did not appear to decline until three months later. The effectiveness of a three-month dose regimen was slightly higher, at about 82%. The researchers theorize that doses three months apart may be the optimal timing, as efficacy was lower in those who received doses just six weeks apart. As other research has shown, no coronavirus-related hospitalizations were found in the vaccinated after 21 days and the vaccine was well tolerated.
The longevity of the protection offered by a single dose is especially reassuring, as the UK has allowed doctors to delay the administration of the second dose to people for up to 12 weeks, or about three months, in order to extend the limited supply of vaccines. Some scientists had worried that a delayed-dose strategy would lead to weakened or short-term protection for some, and countries including the United States have so far chosen not to follow the UK’s example for their licensed vaccines. , citing the lack of evidence on their safety. While other data should be collected to confirm this trend, including other vaccines with a two-dose course, it is a sign that a delayed dose may not be too risky, at least for the Oxford / AstraZeneca vaccine.
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Many scientists have been careful to point out that these vaccine trials have only clearly shown that they are effective in preventing the disease from the virus, not in preventing the transmission of a vaccinated person to an unvaccinated person. However, other experts do he argued that it would be very unlikely that a vaccine would reduce the risk of the first, but not the second. Although there have been some early tests that other vaccines, such as the Pfizer / BioNTech trait, effectively reduce transmission rates, vaccine trials against Oxford / AstraZeneca have been explicitly testing this possibility from the outset.
UK trial volunteers were regularly caught by the virus using PCR tests. Compared to volunteers who had received a placebo shot who were later infected and identified by testing, the vaccinated ones did., on average, 67% less likely to have noticeable levels of the virus in your system, minfection by separation. A lower risk of infection a vaccinated people should do the same it means they are less likely to transmit the virus. Again, this is something that will need to be confirmed by more data from other trials and vaccines. But if that were true, it would obviously be great news to end the pandemic as quickly as possible.
There are still questions about how the spread of new virus variants will affect the effectiveness of these vaccines (so far, it is believed that no variant is likely to completely escape the immunity provided by the vaccine). Beyond science itself, the supply and distribution of these vaccines remains suboptimal, especially in lower-income countries. But there are also signs of improvement.
Last week, the EU authorized the emergency use of the Oxford / AstraZeneca vaccine, following UK authorization last December. The U.S. Food and Drug Administration is also expected to decide whether to allow a single-dose Johnson & Johnson vaccine in the coming weeks (a decision on the Oxford / AstraZeneca vaccine is likely to follow after the trial in the US in the spring). And just today, COVAX, an organization supported by several intentional public health groups and the United Nations, announced its distribution forecast for the AstraZeneca / Oxford vaccine.
During the first and second half of 2021, it plans to distribute more than 330 million doses to 145 countries, along with 1.2 million doses of the Pfizer / BioNTech vaccine. These shipments are expected to cover only about 3% of the people in these countries, but are expected to be enough to cover some of the most vulnerable groups, such as health workers.