Study shows vaccines work but fails to quell Delta variant concerns


AstraZeneca PLC (LSE:AZN) and Pfizer (NYSE:PFE) Inc’s vaccines provide good protection against most variants of the Covid-19 virus according to a new study but may not halt the spread of the infection.

Two doses of the Pfizer and AstraZeneca vaccines provide protection levels at 75% and 61% after three months, though after 4-5 months the efficacy was similar according to a study of 3mln swabs by Oxford University in the largest study of vaccine effectiveness so far.

Both vaccines were less effective against the Delta variant that is currently spreading rapidly across the globe than the Alpha or UK variant, the study found.

Other findings were that the time between vaccines is not important and younger people get more protection than the elderly.

“Both of these vaccines, at two doses, are still doing really well against Delta … When you start very, very high, you got a long way to go,” said Sarah Walker, said the survey’s chief investigator.

Viral load

One important finding in the study is that people who have been vaccinated but catch the Delta variant of Covid-19 have a similar viral load as people who have been vaccinated, suggesting it can be just as contagious whereas the viral load with other variants dropped significantly after vaccination.

Dr Koen Pouwels, one of the lead researchers of the study, said: “The vaccines are better at preventing severe disease and are less effective at preventing transmission.

“The fact that you see more viral load (with the Delta variant) hints towards herd immunity being more challenging.”

Walker added “We don’t yet know how much transmission can happen from people who get COVID-19 after being vaccinated – for example, they may have high levels of virus for shorter periods of time.

“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.”

Concern over the possibility of another wave of Covid-19 infections especially in Asia and the US helped sparked a wave of selling on the stock market today.

FTSE 100 was down around 2% Thursday wiping GBP50bn off its value as investors worried about the impact of additional lockdown measures being imposed, especially in places such as China if the Delta variant continues to spread.


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