No, vaccinated people are not “as infectious” as unvaccinated people if they receive COVID

The Conversation

Some recent studies have shown similar peak virus loads in vaccinated people compared to unvaccinated people who contract COVID. This has aroused concerns about the effectiveness of vaccines in preventing transmission.

How careful should we be? Are vaccinated people as contagious as unvaccinated? What does this mean for future plans for reopening?

These studies only show a similarity pinto virus load, which is the highest amount of virus in the system during the study.

But vaccinated people clean up the virus faster, with lower levels of virus overall, and have less time with very high levels of virus present.

Therefore, vaccinated people, on average, are likely to be less contagious.

Let’s explain.

Similar peak virus loads

A study in the medical journal The Lancet followed 602 main close contacts of 471 people with COVID. It documented transmission and virus loading in the group.

He found that there were no differences in pinto virus loads between vaccinated and unvaccinated individuals. It also showed only a small decrease in the number of infections in domestic members among vaccinated and unvaccinated people, suggesting a similar level of infection.

Another unpublished preview, which is still being reviewed by other scientists, suggests a similar trend in virus load among vaccinated and unvaccinated people, as well as a CDC report in the U.S. in July that analyzed Massachusetts outbreak data.

The Massachusetts data came from a number of major public events over a two-week period in July in Barnstable County, Massachusetts. Of 469 COVID cases, 346 (74%) occurred in fully vaccinated individuals. Virus load was similar in both vaccinated and non-vaccinated groups.

However, let us not be too afraid of this analysis. The reported data are an imperfect representation of the population, and the measures they used – a single swab and PCR test – do not provide information on total virus load over time.

What is a virus load?

Viral load refers to the amount of virus present in one’s body fluids at a given time. Scientists can measure this by looking at your blood, or more often in COVID, swabs from your nose and throat.

In general, higher virus loads are thought to correspond to a more contagious individual.

However, this is not always clear in reality. For example, some people with COVID who have no symptoms and have low virus loads transmit more because they are less likely to follow social distancing, wear masks, and stay home.

The evidence for how viral load relates to severity of disease is mixed. Some studies find no relationship between the amount of virus in swabs and worse results, but others find an increased mortality rate with increasing virus load.

Vaccinated people get rid of the virus faster

The results of the Lancet study suggest similarities in terms of virus load between vaccinated and unvaccinated people. But the study does not provide strong evidence that vaccines do not work to prevent transmission across the population.

While the pinto load may be similar, vaccinated people are likely to have a lower virus load overall, and will therefore be less contagious.

Considering vaccines accelerate the elimination of COVID from the body, vaccinated people have less chance of spreading the virus overall.

This seems to be the case even with the more infectious Delta variant.

While the Lancet study specifically collected an even number of vaccinated and unvaccinated infections to compare them, this is not a true representation of the community in Australia. We know that being fully vaccinated reduces the likelihood of catching COVID even if the vaccines are not perfect (none are) and there are breakthrough infections.

Although it is difficult to estimate the rate of breakthrough infections accurately, studies have estimated that they occur in 0.2% to 4% of people. In fact, this means that for every 100 vaccinated people, somewhere between 0.2 and 4 of them would receive COVID.

So, while in the rare case where a breakthrough infection occurs, there may be a similar virus load, and possibly a similar infection, there remain far fewer vaccinated people getting COVID.

Importantly, while the Lancet study also showed a similar rate of domestic transmission among the vaccinated and unvaccinated, there are a number of other studies in different contexts showing a decrease in transmission through vaccinated people.

So what does it mean for us?

If you are one of the unlucky few vaccinated people who get a breakthrough infection, that means you need to follow the health tips given to you.

Although you may not feel sick, you still have the ability to spread the virus to a vulnerable person around you. Although if the people in your home are also fully vaccinated, then the risk of transmission decreases even more.

However, a vaccinated person is less likely to get COVID in the first case, is less contagious, and is contagious for a shorter time, resulting in significantly less spread of the virus through a highly vaccinated community.

This, combined with the known ability of vaccines to keep people out of hospital and ICU, makes them the most important part of the health response in the near future.

As the vaccine spread continues, and there are fewer people without protection, the declining rate of a new infection will help secure a future where COVID no longer dominates the news, society, and our minds.

Jack Feehan, Research Officer – Immunology and Translational Research, Victoria University and Vasso Apostolopoulos, Professor of Immunology and Associate Provost, Research Partnerships, Victoria University

This article is republished by The Conversation under a Creative Commons license. Read the original article.

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