Early data suggests AstraZeneca Shot may reduce risk of transmission

New research suggests that the covid-19 vaccine developed by AstraZeneca and the University of Oxford will not only provide protection against the symptoms of the viral illness, but also reduce the risk of transmitting the virus to others. Although scientists have been optimistic that this and other covid-19 vaccines would reduce the risk of transmission, the new data is one of the first direct evidence to support this hypothesis.

Researchers at the University of Oxford in the UK released this week’s data in a pre-print paper for the Lancet. Pre-prints are preliminary research documents that have not yet gone through the formal peer review process, so all findings should be viewed with some caution. Regardless, the results of their study – an analysis of longer-term data from clinical trials of the vaccine in the UK and Brazil – seem 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 the immune system takes 21 days). to develop an effective response against the virus). Importantly, the effectiveness did not seem to drop until three months later. The effectiveness of a two-dose regimen three months later was slightly higher, at about 82%. It is possible, the researchers theorize, that doses three months apart would be the optimal schedule, because efficacy was lower in those who received doses only six weeks apart. As other research has shown, no coronavirus-related hospitalizations were found in people vaccinated after 21 days, and the vaccine was well tolerated.

The longevity of protection offered by a single dose is particularly reassuring, as the UK has allowed doctors to delay the administration of the second dose for up to 12 weeks, or around three months, in order to expand the supply limited in vaccines. Some scientists feared that a delayed-dose strategy would result in weakened or short-lived protection for some, and countries, including the United States, have so far not chosen to follow the Kingdom’s lead. United for their licensed vaccines, citing a lack of evidence of its safety. . Although more data needs to be collected to confirm this trend, including for other vaccines with a two-dose cycle, it is a sign that a delayed dose may not be too risky after all, at least for the Oxford / AstraZeneca vaccine.

Many scientists have been careful to note that these vaccine trials have so far not clearly shown that they are effective in preventing disease caused by the virus, and not in preventing transmission from a vaccinated person to a non vaccinated. Yet other experts have argued that a vaccine would be very unlikely to reduce the risk of the first but not the second. Although there have been early proof As other vaccines, such as the Pfizer / BioNTech vaccine, do indeed lower transmission rates, the Oxford / AstraZeneca vaccine trials have explicitly tested this possibility from the start.

Volunteers in the UK trial were routinely sampled for viruses through PCR testing. Compared with volunteers who received a placebo vaccine who subsequently became infected and were identified by testing, the, on average, 67% less likely to have significant levels of virus in their system, meaning infection. Lower risk of infection vaccinated people should also means they are less likely to transmit the virus. Again, this is something that more data from other trials and vaccines will need to confirm. But if this is true, that 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, variants are unlikely to completely escape the immunity provided by the vaccine). Beyond the science itself, the supply and distribution of these vaccines continues to be sub-optimal, especially in low-income countries. But there are also signs of improvement.

Last week the EU authorized emergency use of the Oxford / AstraZeneca vaccine, following the UK authorization last December. The U.S. Food and Drug Administration is also expected to decide whether or not to clear the Johnson & Johnson single-dose vaccine in the coming weeks (a decision on the Oxford / AstraZeneca vaccine will likely follow after the U.S. trial ends in the spring). And just today, COVAX, an organization backed by several intentional public health groups and the United Nations, ad its distribution forecast for the AstraZeneca / Oxford vaccine.

In the first and second half of 2021, it plans to distribute more than 330 million doses in 145 countries, as well as 1.2 million doses of the Pfizer / BioNTech vaccine. These shipments are only expected to cover around 3% of the population of these countries, but it is hoped that this will be enough to cover some of the most vulnerable groups, such as healthcare workers.