New data show that an unboosted Pfizer vaccine may not effectively fight infection from the latest COVID-19 variant.

A large-scale analysis in South Africa found that getting the Pfizer vaccine had limited effects in avoiding an omicron variant infection but better protection against hospitalization. This new data reflect a growing wave of omicron within South Africa.

Medical officials found that the current two-dose Pfizer vaccine provided only 33% protection against infection by the omicron variant but 70% protection against hospitalization.


The analysis, which Discovery Health published in partnership with the South African Medical Research Council, looked at more than 211,000 positive COVID-19 test results in South Africa.

An estimated 41% of the test results came from adults who had received two doses of the COVID-19 vaccine, says Discovery Health. About 78,000 of the positive test results were attributed to omicron.

The data were initially gathered in the first few weeks after South African medical officials had reported the omicron variant. Since then, the number of omicron infections has escalated significantly.

“Superb genetic surveillance by the Network for Genomic Surveillance in South Africa identified that omicron infection accounts for over 90% of new infections in South Africa and has displaced the formerly dominant delta variant,” claims Dr. Ryan Noach, chief executive of South African insurance provider Discovery Health.

South Africa's seven-day rolling average of daily new cases has risen significantly in the last few weeks. The daily estimate moved from 8.07 new cases per 100,000 persons as of Nov. 29 to 34.37 new cases per 100,000 persons on Dec. 13, according to Johns Hopkins University. The death rate has not changed, however.

Discovery Health's study also found that the risk of reinfection is significantly higher with omicron. However, the risk of hospitalization is still lower.


The omicron variant has spread worldwide since it was declared a variant of concern by the World Health Organization. The virus has been reported to be highly infectious but less fatal than previous variants. The first omicron-affiliated death was reported on Monday by British Prime Minister Boris Johnson.

Several cases of omicron have been reported in the United States.

Preliminary tests from Pfizer imply that receiving a vaccine booster shot significantly decreases the chances of someone getting infected by the virus.