Pfizer vaccine less effective against South African variant, Israeli study finds

An Israeli study has indicated the Pfizer-BioNTech COVID-19 vaccine is less effective against the so-called South African variant of the virus.

The study by scientists from Ben-Gurion University of the Negev said that the vaccine produces high levels of antibodies that efficiently combat both the generic strain of the virus and the British variant.

The vaccine only moderately neutralized the South African variant, however. It was also less effective against strains that had attributes of both the British and the South African variants.

The researchers collected blood samples from 10 people who recovered from COVID-19, five people who received the first dose of the vaccine, and 10 people who also received the second. Samples were drawn from participants 21 days after the first dose, or 10 days after the second.

They then measured the antibodies’ ability to protect against infection.

“Our study validates the clinical efficacy of the Pfizer vaccine, but raises concerns regarding its efficacy against specific SARS-CoV-2 circulating variants,” the authors wrote. “Overall, these results call for a close attention of variant spread, and a [possibility] for new vaccines with improved neutralizing potency against SARS-CoV-2 variants.”

SARS-CoV-2 is the name of the coronavirus that causes the disease COVID-19.

“Our findings show the vaccine is less effective against the South African strain, but the efficacy still exists,” said lead researcher Ran Taube.

The study said antibodies of people who have received vaccines appear more resistant to the virus, including its variants, than antibodies of people who recovered from the virus.

Vials of the Pfizer-BioNTech COVID-19 vaccine at Ichilov Hospital in Tel Aviv, December 20, 2020. (AP Photo/Ariel Schalit)

The spread of the variants was likely due to their higher levels of infectivity, and not resistance to vaccines, they said.

The researchers found an elevenfold increase in antibody levels for people who had completed vaccine treatment relative to people who had recovered from the virus, and far higher levels than for people who had only received the first vaccine dose, suggesting the full treatment is necessary for a high level of protection.

People who recovered from the virus were also less protected against the South African strain than the British variant.

The authors said people who had been infected by the South African variant were probably unlikely to get reinfected by the same variant.

The study used pseudoviruses, or a laboratory-safe virus particles that do not replicate, presenting a possible limitation to the results. The use of pseudoviruses for evaluating antibodies was previously established and earlier studies of the SARS-CoV-2 virus validated the use of pseudoviruses in research, the authors noted.

The study was published on Saturday in the peer-reviewed scientific journal Cell Host & Microbe. The researchers are from Ben Gurion University’s Shraga Segal Department of Microbiology and Immunology.

Israel’s vaccine campaign, which has vaccinated most eligible adults, relies mostly on the Pfizer vaccine.

The entrance of vaccine-resistant variants has been a top concern for Israeli officials and spurred the government to tightly limit international travel for much of the pandemic, including a months-long shutdown of Ben Gurion Airport, even to most Israeli citizens.

Most infections in Israel are caused by the British strain of the virus.