Pfizer jabs protect against Omicron hospitalisations, first study shows

Pfizer vaccines protect against the Omicron variant of Covid-19, with two doses offering 70% protection against admission to hospital, a large real world study by Discovery Health and the SA Medical Research Council shows (SAMRC).

This is the first study to show that the risk of hospitalisation is lower during the Omicron-driven fourth wave in SA than it has been in previous waves, relative to the numbers of infections.

The new analysis finds there is a 29% lower overall hospital admission risk linked to Omicron infection among the general population compared to the first wave of infections in 2020, Discovery revealed at a briefing on Tuesday.

Discovery Health CEO Dr Ryan Noach said people who were fully vaccinated with Pfizer-BioNTech shots had “high levels of protection from serious illness across age groups and in the face of a range of chronic illness”.

This does not mean Omicron is a less virulent strain of the virus, SAMRC president Prof Glenda Gray cautioned during the briefing.

The lower rate of hospital admissions during the fourth wave of infections could be related to the population having greater immunity from earlier infections and Covid-19 vaccinations than in previous waves.

“SA has quite a high seroprevalence of prior infection, particularly after Delta, and in some parts of SA up to 80% of people were exposed to previous infection. That together with just under 40% vaccination coverage could have resulted in a wave that appears to be delinked from hospitalisation.

“However, we do not know how Omicron is going to evolve in countries where there are lower vaccination rates or higher infection rates.”

The rate of reinfection with the Omicron variant is “relatively high” among those who have previously been infected with other variants of Covid-19 this year, the researchers found.

The effectiveness of the double-dose Pfizer vaccine against becoming infected dropped from 80% against previous variants to only 33% against the Omicron variant.

Noach also noted the absolute number of paediatric admissions were low but the risk of admission was higher to date than in the first wave.

“The Omicron variant may pose a risk of greater severity to children under 18. There is a 20% higher admission rate relative to in the first wave but the admission rate itself is low,” said Noach, noting admissions were “settling down” as the wave progressed.

About 78,000 pathology test results, vaccination results and clinical results from Discovery Health’s data from November 15 to December 7 were the basis of this research.

Discovery’s health informatics analysts, led by chief health analytics actuary Shirley Collie, teamed up with Gray and SAMRC scientists to conduct the study.

Noach noted the preliminary results could change over time, given that these findings are limited to the first three weeks of the Omicron wave.

The Omicron variant, identified late in November, is driving SA’s fourth wave of infections and is highly transmissible. But as the latest analysis confirms, hospital admissions have so far been significantly lower and decoupled from the pace of infections in this wave.

When SA scientists shared their information about the Omicron variant internationally, world leaders responded with panicked and unscientific travel bans.

The clinical reports and data collected suggest the Omicron-driven wave in SA may be resulting in the mildest symptoms seen until now.

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