Small efficacy trial doesn’t show whether vaccine may prevent severe disease caused by antibody-dodging strain
www.sciencemag.org
But the J&J vaccine, which was put to the test in the largest of the studies, convincingly protected against severe disease and death, even against the B.1.351 variant, and Madhi remains “somewhat optimistic” that the AstraZeneca-Oxford vaccine will, too; the results are not “all doom and gloom,” he said.
SARS-CoV-2–targeting antibodies triggered by the J&J vaccine were “very similar,” he said, to those elicited by the AstraZeneca-Oxford candidate, and the two vaccines are based on a similar technology: Both induce the body to make the spike surface protein of SARS-CoV-2 by delivering its genes in a harmless adenovirus. In a 44,000-person trial, the J&J vaccine prevented 85% of severe cases and completely protected people from hospitalization and death in several countries, including the 15% of the participants who were from South Africa.
Madhi and the research team had planned to report the results tomorrow, but the Financial Times ran a story on Saturday based on a leaked copy of the findings. Madhi and his co-workers have submitted a paper describing their data to a preprint server and expect it will post tomorrow.
The AstraZeneca-Oxford vaccine has produced
confusing results from the start. Earlier preliminary results from trials in different countries showed a wide range of success rates against mild and moderate disease, but researchers have had difficulty interpreting the data because of differences in dose, intervals between doses, and variants in circulation. Just on Friday, a study suggested the vaccine offered
strong protection against a more transmissible variant, B.1.1.7, that exploded in the United Kingdom and is now spreading fast throughout Europe.
In South Africa, the vaccine was given in two doses spaced 21 to 35 days apart. Antibodies made by vaccine recipients can typically “neutralize” SARS-CoV-2, meaning they can prevent it from infecting cells in culture experiments. But lab studies show they have far less power against B.1.351.
Madhi stressed that the vaccine may still trigger a powerful T cell response, which can target and eliminate cells the variant manages to infect. He presented a test tube study showing how the mutations in the spike protein that allow B.1.351 to dodge neutralizing antibodies have little impact on T cell responses. “We believe that those T cell responses will still remain intact despite the mutations that exists in a B.1.351 variant,” Madhi said.
