Two doses of Pfizer-BioNTech's COVID-19 vaccine appear to have given 70% protection against hospitalization in South Africa in recent weeks, a major real-world study on the potential impact of Omicron showed on Tuesday, as the country battles a spike in infections linked to the new variant.
The study released by South Africa's largest private health insurance administrator, Discovery Health, was based on more than 211,000 positive COVID-19 test results from Nov. 15 to Dec. 7, around 78,000 of which were attributed to Omicron.
The 78,000 results are not confirmed Omicron cases, meaning the study is not able to draw conclusive findings about the variant labeled "of concern" by the World Health Organization.
South African scientists have so far confirmed around 550 Omicron sequences, with the variant accounting for 78% of sequences from November, more than the previously dominant Delta variant.
South Africa alerted the world to Omicron late last month, triggering an alarm that it could cause another surge in global infections, and lead to the imposition of travel restrictions on southern Africa. South Africa's daily infections have since risen to around 20,000 in recent days.
Based on analysis by Discovery's clinical research and actuarial teams, and in collaboration with South Africa's Medical Research Council (SAMRC), the real-world study calculated that two doses of Pfizer-BioNTech offered 70% protection against hospitalization during the recent surge in cases and 33% protection against infection.
South Africa is using the Pfizer-BioNTech and Johnson & Johnson vaccines in its COVID-19 immunization campaign, with more than 20 million Pfizer doses administered so far.
It concluded that there was a higher risk of reinfection during the fourth wave than during previous waves and that the risk of hospitalization among adults diagnosed with COVID-19 was 29% lower than during the country's first wave early last year.
Children appeared to have a 20% higher risk of hospital admission with complications during the fourth wave than during the first, despite a very low absolute incidence, it said.
Discovery cautioned that the study's findings should be considered preliminary.
Glenda Gray, SAMRC president, said it was important that the Pfizer-BioNTech vaccine appeared to be offering good protection against severe disease and hospitalization.