The effect of the vaccines on transmission of Covid-19 — Another use Case for ClinTex CTi?
In order to control the pandemic, the vaccines need to prevent the spread of the virus. But the data on this is not clear, and clinical studies to collect data on this is largely disjointed and “data collaboration” is poor — a problem addressed by the CTi platform.
As countries roll out vaccines that prevent COVID-19, studies to collect data are under way to determine whether shots can also stop people from getting infected and passing on the SARS-CoV-2 virus. Vaccines that prevent transmission could help to bring the pandemic under control if they are given to enough people.
Preliminary analyses suggest that at least some vaccines are likely to have a transmission-blocking effect. But confirming that effect — and how strong it will be — is tricky because a drop in infections in a given region might be explained by other factors, such as lockdowns and behaviour changes. Not only that, the virus can spread from asymptomatic carriers, which makes it hard to detect those infections.
Although most clinical trials of COVID-19 vaccines showed that vaccines prevented the disease, some trial results also offered clues that shots might prevent infection. A vaccine that is highly effective at preventing people from acquiring the infection in the first place would help to reduce transmission. During the trial of Moderna’s vaccine, produced in Boston, researchers swabbed all participants to see if they had any viral RNA. They saw a two-thirds drop in the number of asymptomatic infections among people who received the first shot of the two-dose vaccine, compared with those who received a placebo. But they tested people only twice, about a month apart, so might have missed infections.
The UK trial of the vaccine produced by the University of Oxford and AstraZeneca swabbed participants every week, and estimated a 49.3% reduction in asymptomatic infections among a subset of vaccinated participants compared with the unvaccinated group. Pfizer, based in New York City and maker of another leading COVID-19 vaccine, says that it will start swabbing participants every two weeks in vaccine trials taking place in the United States and Argentina, to see whether the shot can prevent infection.
As part of an ongoing study of hundreds of health-care workers in England, known as PANTHER, researchers at the University of Nottingham tested health-care workers and the people they lived with for SARS-CoV-2 antibodies and viral RNA between April and August last year, around the time of the first pandemic wave. They will now retest some of those workers after they receive the Pfizer vaccine, as well as their close contacts who won’t have been vaccinated, to see whether the risk of infection has decreased for the close contacts. If the risk decreases, that would mean the vaccines are probably preventing transmission.
Other groups, in Israel, are also planning to study households in which one member has been vaccinated. If these people become infected, researchers can see whether they pass on the virus to other household members.
In Brazil, a trial will randomly distribute doses of the COVID-19 vaccine produced by the Beijing-based drug company Sinovac to the town of Serrana in stages over several months. This approach could show whether drops in COVID-19 in vaccinated regions also contribute to reduced transmission in unvaccinated areas. This would demonstrate the indirect effects of vaccines.
These are just some of the many studies of individuals and larger populations that are needed to see how well vaccines protect against transmission, generating a wealth of data that is disjointed and has poor interoperability — an ongoing issue that ClinTex CTi will address.
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