Delta variant in SA: Why getting your second shot of the Pfizer vaccine is so important

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  • The Delta variant is of major concern, but being fully vaccinated considerably increases protection
  • As soon as it is available, people should get their second shot of the Pfizer-BioNTech vaccine
  • Research shows that getting both doses decreases hospitalisation with the Delta variant

South Africa's Covid-19 vaccine rollout programme is underway, with members of the public eligible for the shot so far getting the two-dose Pfizer-BioNTech injection.

Currently, the plan is for injections to be administered six weeks apart, after an initial plan to have a three-week gap between shots.

South Africa is now under pressure from the third wave of Covid-19 infections, and the latest news indicating that the Delta variant is playing a big role in driving new infections is cause for concern.

Why both doses are needed  

For those who have already had their first Pfizer-BioNTech shot, and may be considering missing the second dose, don't do it.

And here's the evidence why: To enjoy the best level of protection against Covid-19, and especially the Delta variant, both doses are needed.

According to laboratory data – from the Francis Crick Institute and the National Institute for Health Research (NIHR) UCLH Biomedical Research Centre, published in The Lancet as a research letter – researchers found that levels of antibodies in the blood of vaccinated people that can recognise and fight the Delta variant are on average lower than those against previously circulating variants in the UK – like Alpha (first discovered in the UK) and Beta (first discovered in South Africa.

This finding shows that the concern around the Delta variant is warranted.

Much lower protection with only one dose of Pfizer vaccine

Researchers analysed antibodies in the blood of 250 healthy people who received either one or two doses of the Pfizer-BioNTech Covid-19 vaccine, up to three months after their first dose. 

According to a press release, the researchers found that in people who had been fully vaccinated with two doses of the Pfizer-BioNTech vaccine, levels of neutralising antibodies were more than five times lower against Delta when compared to the original Covid-19 virus strain, upon which current vaccines are based.

The researchers said, that, even more importantly, the antibody response was lower even in people who had only received one dose of the Pfizer-BioNTech.

After a single dose of Pfizer-BioNTech, they said, 79% of people had a quantifiable neutralising antibody response against the original strain of the virus.

But in the case of variants, in people vaccinated with just a single dose, this fell to 50% for the Alpha variant (first discovered in the United Kingdom), 32% for the Delta variant, and 25% for Beta (first discovered in South Africa).

This emphasises why getting a second dose of the Pfizer-BioNTech vaccine will be of the utmost importance, even if people are proving to have lower neutralising antibodies with the Delta variant.

Additional concerns

The researchers were, however, cautious to point out that neutralising antibodies alone should not be the marker for vaccine protection.

"Although laboratory results such as these are needed to provide a guide as to how the virus might be evolving to escape the first generation of vaccines, levels of antibodies alone do not predict vaccine effectiveness and prospective population studies are also needed.

"Lower neutralising antibody levels may still be associated with protection against Covid-19."

The scientists said that this is the largest study to date to investigate vaccine-induced antibody neutralising capacity against the newest variants of concern in healthy adults.

Additional concerns were raised as antibody levels were shown to be lower with increasing age. These levels, according to the research, also decline over time, which the scientists said backed plans for booster shots for vulnerable groups.

Further evidence of protection of two doses

A preprint analysis from Public Health England further supports the protection from having both doses of the Pfizer-BioNTech vaccine.

The findings suggest that with the Delta variant, the Pfizer-BioNTech vaccine is 96% effective against hospitalisation after two doses, which the researchers said was comparable with vaccine effectiveness against hospitalisation as a result of the Alpha variant.

More than 14 000 cases of the Delta variant were looked at in the study, of which 166 people were admitted to hospital. Researchers looked at emergency hospital admissions in England between 12 April and 4 June.

In a press release, head of immunisation at Public Health England, Dr Mary Ramsay, said the findings were hugely important, and confirmed that vaccines (the study also looked at the effectiveness of the AstraZeneca vaccine) offer significant protection against hospitalisation resulting from the Delta variant.

"The vaccines are the most important tool we have against Covid-19. Thousands of lives have already been saved because of them.

"It is absolutely vital to get both doses as soon as they are offered to you, to gain maximum protection against all existing and emerging variants," she said.

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