South African Study Finds That Pfizer Only Provides Partial Protection Against Omicron

Posted on the pre-print repository medRxiv on Tuesday, also found that considerable immunity is retained in people who were both vaccinated and previously infected.

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New Delhi: A yet to be peer-reviewed lab study suggests that the Pfizer vaccine provides less protection from the Omicron variant of the coronavirus than other variants but a booster may still provide better protection. 

Posted on the pre-print repository medRxiv on Tuesday, also found that considerable immunity is retained in people who were both vaccinated and previously infected.

The study says that the emergence of Omicron has raised concerns that, based on a large number of mutations in the spike protein and elsewhere on the virus, this variant will have a considerable escape from vaccine-elicited immunity. The SARS-CoV-2 virus uses the spike protein to enter and infect human cells.

"The clinical implications of these important laboratory data need to be determined. It is likely that lesser vaccine-induced protection against infection and disease would be the result," said Professor Willem Hanekom, executive director at Africa Health Research Institute, South Africa, reported PTI.

"Importantly, most vaccinologists agree that the current vaccines will still protect against severe disease and death in the face of Omicron infection. It is therefore critical that everyone should be vaccinated," Hanekom said in a statement.

They tested 14 plasma samples from 12 participants, with six having no previous record of SARS-CoV-2 infection nor detectable antibodies indicative of the previous infection. The remaining six participants had a record of previous infection in the first SARS-CoV-2 infection wave in South Africa where the infection was with ancestral D614G variant.

The researchers investigated whether Omicron escapes antibody neutralisation elicited by the Pfizer mRNA vaccine and if the virus still requires binding to the ACE2 receptor on human cells to infect them. They used a human lung cell line clone engineered to express the ACE2 receptor to both isolate the virus and test neutralisation.

The research finding indicated that ACE2 is required for Omicron entry. The researcher also tested the ability of plasma from Pfizer vaccinated study participants to neutralise Omicron versus ancestral D614G virus.