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New research finds vaccinated people are less likely to spread Covid-19

Photo credit: Eva Marie Uzcategui / Bloomberg via Getty Images. A health care worker administers a dose of a Covid-19 vaccine in Miami on Aug. 5, 2021.

Learning to live with the Covid-19 is now a reasonable goal and vaccines remain our best protection. This will also require citizens across the world to be more receptive to Covid-19 vaccination, governments helping to increase access to vaccines to poorer countries, educating the population about Covid-19 and dealing with myths and misinformation about the vaccines to reduce public anxiety on vaccination.

A clear picture is unfolding, the vaccines are broadly safe and they are effective in reducing severe illness and hospitalisation of those infected with the SARS-CoV-2. Recent data from New York City show that more than 96 percent of cases are among the unvaccinated. Only 0.33 percent of fully vaccinated New Yorkers have been diagnosed with Covid-19 (Craig Spencer, 2021). Significantly, a latest study indicates that people who are fully vaccinated against Covid-19 are less likely to spread the virus even in breakthrough infection cases.

The first studies to specifically investigate how well vaccines prevent the spread of SARS-CoV-2 carried out by the UK and the US researchers add to a growing body of evidence that vaccines can reduce transmission of the Delta variant; the studies indicate that people who become infected with the Delta variant are less likely to pass the virus to their close contacts if they have already had a Covid-19 vaccine than if they have not. However, the scientists also found that the protective effect is relatively small, and wanes significantly three months following the second shot (Akshay Syal, 2021).

After three months, people who had breakthrough infections after being vaccinated with AstraZeneca were just as likely to spread the delta variant as the unvaccinated. While protection against transmission decreased in people who had received the Pfizer vaccine, there was still a benefit when compared with people who were unvaccinated.  

In the yet to be peer-reviewed real-world transmission study, British researchers at the University of Oxford examined national records of nearly 150,000 contacts that were traced from roughly 100,000 initial cases. The samples included people who were fully or partially vaccinated with either the Pfizer-BioNTech or the AstraZeneca vaccines, as well as people who were unvaccinated. The researchers then looked at how the vaccines affected the spread of the virus if a person had a breakthrough infection with either the alpha variant or the highly contagious delta variant,( Akshay Syal, 2021).

According to Akshay Syal (2021) the findings from the UK study indicated that both vaccines reduced transmission, although they were more effective against the alpha variant compared to the delta variant. The same study found that when infected with the delta variant, a given contact was 65 percent less likely to test positive if the person from whom the exposure occurred was fully vaccinated with two doses of the Pfizer vaccine. But with AstraZeneca, a given contact was 36 percent less likely to test positive if the person from whom the exposure occurred was fully vaccinated.

It is worth highlighting that the researchers found that the risk of transmission from a breakthrough infection was much higher if someone had received just a single dose of either vaccine.

The research also confirmed previous studies findings that found a similar level of viral load in unvaccinated and vaccinated people who were infected with the Delta variant; significantly, people who were fully vaccinated were still less likely to infect others.

Scientists point to a likelihood that people who have been vaccinated clear the infectious virus from the body quicker. The argument is backed by findings from a previous study (cited by Tara Parker-Pope, 2021) from Singapore which found that although levels of the virus were initially the same in those infected with the delta variant regardless of vaccine status, by day seven, levels of the virus dropped quickly in those who were vaccinated, which may reduce the ability to spread illness.

There is emerging body of evidence that even though cycle threshold values may be the same regardless of vaccination status, people who are vaccinated may have less infectious virus in their bodies, potentially reducing transmission (Richterman, 2021). A recent pre-print from China found a large reduction in transmission in those who had received two doses of vaccine, compared to the unvaccinated.

We can thus argue with a high degree of confidence that to date vaccines have shown an ability to prevent transmission by reducing the amount of infectious virus in the vaccinated people.

Richterman (2021) argues, “People who have been vaccinated will have immune systems at the ready that can coat the virus in antibodies much more quickly than unvaccinated people who have to build up an immune response”.

Vaccination is our best bet to going back to ‘normal life’. We do acknowledge vaccines are not perfect, while they have been effective in reducing severe illness and hospitalisation thereby freeing up beds for use for other medical conditions, they have not been able to stop infection and transmission of the SARS-CoV-2 from vaccinated people. However, evidence indicates transmission from vaccinated individuals is reduced compared to the unvaccinated. Our recommendation to Matabeleland citizens would be: get vaccinated, if unsure or you have underlying conditions, talk with your physician for further advice.  


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