Pharmaceutical giant Pfizer will ask US regulators to authorise a booster dose of its COVID-19 vaccine within the next month. On Thursday, Jul 8th, the company’s lead scientist said the request is due to two main reasons.
Firstly, there is mounting evidence of a greater risk of reinfection six months after full vaccination. Secondly, a booster dose should be given because of the increasing number of cases of the highly contagious Delta variant.
However, a joint statement was issued by the US Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC). The statement said that that fully vaccinated Americans do not need a booster COVID-19 shot at this point in time.
Questioned by scientists
The need for booster shots is being questioned by some scientists.
A case in point
The recent reported drop in the vaccine’s efficacy in Israel is mostly due to infections in people vaccinated in January or February. Mikael Dolsten, Pfizer’s chief scientist provided this data from Israel.
In June, the vaccine’s efficacy in preventing both infection and symptomatic disease fell to 64 percent according to the country’s health ministry.
In an interview, Dolsten said “The Pfizer vaccine is highly active against the Delta variant.” However, he said after six months “there likely is the risk of reinfection as antibodies, as predicted, wane”.
On Thursday, Pfizer did not release the full set of Israeli data, but said it would be published soon.
Dolsten said “It’s a small data set, but I think the trend is accurate: Six months out, given that Delta is the most contagious variant we have seen, it can cause infections and mild disease.”
Efficacy erosion noted
In their joint statement, the CDC and FDA said they are prepared for booster doses. The booster doses will be given, if and when the science demonstrates a need for them.
Dolsten said the vaccine efficacy erodes to the mid-80s against the variants circulating in the spring after six months. This is based on Pfizer’s own data from the United States.
95 percent efficacy
Even with declining antibody levels, the vaccine remains around 95 percent effective against severe disease. Dolsten says this is based on data from Israel and Britain.
Pfizer collaborated with German partner BioNTech to develop and produce the vaccine. It has a 95 percent efficacy in preventing symptomatic COVID-19, as seen in clinical trials the companies ran last year.
What a third dose does
Dolsten said a third booster dose generates antibody levels that are five- to 10-fold higher than after the second dose. He based this on early data from the company’s own studies. This suggests promising protection coming from a third vaccine dose.
Sought by other countries
Pfizer has already been approached by many countries in Europe and elsewhere to discuss booster doses, according to Dolsten. Some of these countries may begin giving out third booster doses before the US authorizes it.
Booster shots are more important for people in the older age groups says Dolsten.
More studies needed
Basing the decision on lower antibody protection ignores the role of important other parts of the immune response, said Dr Eric Topol. Dr Topol is a professor of molecular medicine and director of the Scripps Research Translational Institute in La Jolla, California.
Other parts of immune response includes memory B cells, which can make antibodies on demand when challenged by the virus.
Dr Topol said “You need better studies to be able to assert that. It isn’t just neutralising antibodies.”
There are questions by some scientists on when, or whether, boosters will be needed. However, Pfizer has stated previously that people will likely need a booster dose.
9th July 2021 23:00
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