Narissa Subramoney
Copy rewriter
3 minute read
14 Dec 2021
1:44 pm

Pfizer’s Covid-19 vaccine less effective against Omicron, experts say

Narissa Subramoney

The compounding waning durability of vaccines has provided a clear-cut case for booster shots, says Professor Glenda Gray.

Picture: iStock

New insights from Discovery Health shows there is reduced effectiveness in the two-dose Pfizer Covid-19 vaccine against the Omicron variant.

However, it’s important to note the vaccines were developed to prevent serious illnesses that arise from Covid-19 infections.

According to Discovery’s real-world analysis of the Omicron outbreak in South Africa, the Pfizer-BioNTech vaccine’s effectiveness reduced from 80% during the Delta wave to 33% during the Omicron wave.

At the same time, protection against severe complications reduced from 93% in Delta wave to 70% in Omicron wave.

But Discovery Health CEO Dr Ryan Noach says the severity of infections during the Omicron wave is 29% lower than the first wave.

Discovery’s chief health analytics actuary, Shirley Collie said Pfizer vaccines were 33% effective against Omicron.

“Omicron has materially reduced vaccine effectiveness against new infections, potentially compounded by waning durability,” said Collie.

Booster shots are necessary

The compounding waning durability of vaccines has provided a clear-cut case for booster shots.

According to South African Medical Research Council (SAMRC) president, CEO and co-principal investigator of the Sisonke study, Professor Glenda Gray, boosting strategies may mitigate decreasing efficacy rates by increasing vaccine-induced immune responses.

“In people who don’t have good immune responses, clearing the virus may be prolonged therefore predisposing to immune escape and possible viral evolution,” said Gray.

‘Natural Immunity’ vs vaccines

The jury is out on this one, a hybrid protection cover, which includes the jab after infection, offers greater protection against the virus.

Prior infection with Covid-19 offers the host some “natural immunity”, but Omicron has also reduced the levels of natural protection in the host. So if you were infected with any of the other variants, the natural immunity is not as strong against Omicron.

Children and Omicron

anti-vaxxers fourth wave children hospitalisations omicron
Picture: iStock

Discovery has noted there has been a large number of coincidental findings. This means that children who were seeking medical treatment for other reasons test positive for Covid-19 during routine testing at healthcare centres.

Data shows that Omicron may pose a risk of increased severity to children under 18, while adults experience a 29% lower admission risk.

The most dominant symptoms in Omicron paediatric admissions are bronchiolitis and pneumonia. It is often associated with diarrhoea, vomiting and nausea. To date, children under five years experience a higher admission risk.

“There is a higher number of infections among children. Early symptoms include a sore throat, nasal congestion and fever for 2-3 days. But the infection seems to resolve quickly with recovery after three days.

“Most hospitalisations in this wave are unvaccinated people. There was a much steeper increase in new cases during the first three weeks of the Omicron wave,” said Noach.

There is a fear that the health system can still be overrun with infections if people refuse to get vaccinated. The prevailing hesitancy is evident in the decreased demand for vaccines in the past couple of months.

“The fourth wave now and infections are dominated by the Omicron variant. There’s a higher reinfection and breakthrough infection rate than the other waves,” said Noach.

Gray said research is being done into the efficacy of the Johnson and Johnson single dose against Omicron.

“We are busy looking at that right now. For Sisonke, although we have had lots of breakthrough infections, there have been minimal admissions and as of now no deaths, demonstrating that the vaccine is working against severe disease,” said Gray.