Pfizer claims that a third dose of its vaccine would 'neutralise' the Delta variant

The effectiveness, with two jabs, drops by an average of 6 per cent every eight weeks after the first two months.
The effectiveness, with two jabs, drops by an average of 6 per cent every eight weeks after the first two months. / SUR
  • The American pharmaceutical giant has supplied around 85 per cent of the doses administered in Spain

The American pharmaceutical giant Pfizer has presented its first study to show the impact a third dose of its vaccine could have on the Delta variant, the coronavirus strain that is already dominant in Spain and in most Western countries. Experts say the variant is much more contagious and has greater vaccine escape than its predecessors.

The preliminary data, which was presented to Pfizer investors, and which has not yet been validated by the scientific community, was presented alongside the company’s quarterly financial results.

The document claims a booster jab could "potentially neutralise the Delta variant" and says that its clinical trial shows the third injection can "strongly boost" protection against the strain.

The laboratory pointed out that a third dose produces levels of antibodies against the Delta mutation some 5 times higher in people between 18 and 55 years old and more than 11 times in people between 65 and 85, compared to the levels achieved after two single jabs. Pfizer said their own studies suggest that the booster dose should be administered between 6 and 12 months after the second injection, which is when antibody levels begin to fall, drastically.

CEO Albert Bourla said that their own studies confirm that the effectiveness of its vaccine with just two doses drops to 84 per cent between four to six months after administration. The maximum effectiveness of vaccine prophylaxis is 96.2 per cent, but only in the first couple of months after receiving the two jabs. Then, the effectiveness drops by an average of 6 per cent every two months, according to a study by Pfizer itself, but it has not yet been peer reviewed.

For now, the European Medicines Agency has not concluded its trials on the benefits of this booster dose from Pfizer, the company that is behind 85 per cent of the doses administered in Spain. The EMA's studies are still in their early stages, according to the regulatory officials. “It is too early to decide if a booster dose will be necessary. There is not enough data from the vaccination campaigns and research to know how long the protection of the Covid-19 vaccines will last” the EMA explained at a press conference this month.

The World Health Organization (WHO) has advised against the third dose for the moment, because scientific data "does not justify it for the moment" and it would also "increase inequality" at a time when many developing countries have not yet been able to immunise their most vulnerable populations, warned Dr. Didier Houssin, president of the WHO Emergency Committee for Covid-19.