Covid-19 News

Discovery study finds Pfizer vaccine lowers risk of hospitalisation

Pfizer vaccine efficacy lower against omicron
Written by Health-e News

Discovery Health has released its research on the effectiveness of two-dose Pfizer-BioNTech vaccination in preventing severe disease and hospitalisation by the Omicron variant. The study was carried out by Discovery Health’s actuarial team in collaboration with scientists at the South African Medical Research Council.

The analysis includes more than 211 000 COVID-19 test results, 41% from adult members who had received two doses of the Pfizer-BioNTech vaccine. Approximately 78 000 of these COVID-19 test results were attributed to Omicron infections over the period 15 November 2021 to 7 December 2021.

“We used a test-negative design methodology to establish the Pfizer-BioNTech COVID-19 vaccine’s real-world effectiveness against hospital admission from Omicron infection,” said Shirley Collie, Chief Health Analytics Actuary at Discovery Health. 

The findings of the study were reviewed by scientists at the SAMRC

Pfizer vaccine protects against Omicron

The two-dose Pfizer-BioNTech vaccination provides 70% protection against severe complications of COVID-19 requiring hospitalisation, and 33% protection against COVID-19 infection, during the current Omicron wave.

Before the Omicron wave, it provided 80% protection against infection. Researchers attribute this to lower antibody susceptibility, following the extensive spike protein mutations in the Omicron variant.

The results also show that these same vaccinated people who received two doses of the Pfizer-BioNTech vaccine had 70% protection against hospital admission. The vaccine had provided 93 percent protection against hospitalisation by the Delta variant.

 Researchers say this is still a very good level of protection. President of the SAMRC, Professor Glenda Gray, said the results were very encouraging. 

“It is extremely important to be able to demonstrate to the public that in a real-world setting – in the presence of a highly transmissible new COVID-19 variant – the Pfizer-BioNTech vaccine provides good protection against severe disease and hospitalisation,” said Gray.

Protection against admission is also consistent across a range of chronic illnesses, including diabetes, hypertension, hypercholesterolemia, and other cardiovascular diseases.

Reinfection risk significantly higher

“With each successive wave of COVID-19 infection in South Africa, we have investigated the durability of immunity following the previous infection with COVID-19 – in other words, the risk of reinfection,” explains Collie.

“Overall, the risk of re-infection (following prior infection) has increased over time, with Omicron resulting in significantly higher rates of reinfection compared to prior variants.”

  • People who were infected with COVID-19 in South Africa’s third (Delta) wave face a 40% relative risk of reinfection with Omicron.
  • People who were infected with COVID-19 in South Africa’s second (Beta) wave face a 60% relative risk of reinfection with Omicron.
  • People infected during the first wave face a 73% risk of reinfection relative to those without prior documented infection 

Lower chance of severe disease, hospitalisation 

The risk of hospital admission among adults diagnosed with COVID-19 is 29% lower for the Omicron variant infection compared to infections involving the D614G mutation in South Africa’s first wave in mid-2020.

Collie said adults are experiencing a 29% lower admission risk relative to South Africa’s first wave of infection. 

Those hospitalised now have a lower chance of being admitted to high-care and intensive-care units, relative to prior waves.

Complications among children

Despite very low absolute incidence, preliminary data suggests that children have a 20% higher risk of hospital admission in the Omicron-led fourth wave in South Africa, relative to the D614G-led first wave.

Children continue to show a very low incidence of severe complications following COVID-19, 

But Discovery Health’s data indicates that children under age 18 have a 20% higher risk of admission for complications of COVID-19 when infected with Omicron.

“This is early data and requires careful follow-up. Anecdotal reports from hospitals in South Africa indicate that most COVID-19 diagnoses in children admitted to hospital are co-incidental – many children who are admitted for non-COVID-19-related conditions, and who are not experiencing COVID-19 complications, test positive for COVID-19 on routine screening tests,” said Collie

It is also important to note that Discovery Health’s analysis shows that the risk of children testing positive for COVID-19 infections is significantly lower than in adults.

“Children were 51% less likely to test positive for COVID-19 relative to adults in the Omicron period and, overall, the risk of children being admitted to hospital for COVID-19 complications remains low,” Collie said. – Health-e News

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