Vaccines don’t limit Delta viral load
LONDON • Fully vaccinated people carry the same amount of coronavirus as the unvaccinated, scientists have found, in a new study that calls into question the effectiveness of vaccine passports.
Experts had hoped that two doses of vaccine would significantly reduce the viral load carried by people who became infected, lowering the risk of them passing on the disease.
Previous studies showed that vaccinated people who contracted the Alpha variant had far lower viral loads than the unvaccinated.
But a new study by Oxford University shows that the Delta variant wipes out the viral load reduction.
Instead, even the fully jabbed carry high levels of virus if they become infected, and are also more likely to be symptomatic than vaccinated people who picked up an Alpha infection.
The results suggest that those who are fully jabbed could be as capable of passing on COVID as the unvaccinated, although they are less likely to pick up the disease in the first place.
Sarah Walker, professor of Medical Statistics and Epidemiology at the University of Oxford and chief investigator and academic lead for the COVID-19 Infection Survey, said:
“With Alpha, people with two doses had really low levels of virus.
“When Delta started to come in, the first thing that happened was that the virus values went up and now we really don’t see any difference in the amount of virus people get if they get infected after vaccination.
“Two doses are still protective, you are still less likely to get infected, but if you do, you will have similar levels of virus as someone who hasn’t been vaccinated at all.”
The researchers say they are not sure if high viral load would translate into the same levels of transmission for vaccinated and unvaccinated people, because the fully jabbed may clear the virus quicker, and so be infectious for a shorter period of time.
However, Walker added: “But the fact that they can have high levels of virus suggests that people who aren’t yet vaccinated may not be as protected from the Delta variant as we hoped . ...
“I suspect the higher levels of the virus in vaccinated people are consistent with the fact that unvaccinated people are still going to be at high risk.”
Dr. Koen Pouwels, senior researcher in Oxford University’s Nuffield Department of Population Health, said: ”While vaccinations reduce the chance of getting COVID-19, they do not eliminate it.
“(Our) data shows the potential for vaccinated individuals to still pass COVID-19 on to others and the importance of testing and (self-isolation).”
Two doses of the Pfizer vaccine provided 97 per cent protection against death with coronavirus in nursing home residents, according to a large study, published in The BMJ.