Since the Delta change represents 83% of new COVID-19 cases in the United States, a new study warns that the Johnson & Johnson vaccine may not provide as much protection as the original virus.

Through the study of blood samples, the researchers found that compared with Pfizer and Moderna vaccines, Johnson & Johnson vaccine not only has lower overall efficacy, but also weak against Delta variants. They said a second dose of vaccine might be needed.

“The message we want to convey is not that people shouldn’t be vaccinated against Johnson & Johnson, but we hope that in the future, with another booster from Johnson & Johnson or Pfizer or Moderna, it will be strengthened,” Nathaniel Landau, New York University Virologists at Grossman Medical School told New York Times.

These latest findings contradict the results of a small study previously published by Johnson & Johnson, which reported that the vaccine can provide protection against the variant for up to eight months. Wall Street Journal.

New York University’s research is published online on a preprint server BioRxiv And it has not been peer-reviewed or published in a medical journal.

Because the research relied on laboratory testing, a Johnson & Johnson spokesperson told New York Times It does not reflect the true performance of the vaccine against this variant.

In this study, Landau and his team analyzed blood samples from 17 people who had received two doses of mRNA vaccination and 10 people who had received a single dose of Johnson & Johnson vaccine.

The idea that two doses of the COVID-19 vaccine are better than one dose is not new.A kind Study in the UK A report released in May stated that a single dose of AstraZeneca vaccine is not as effective as two doses of the Delta variant. Even if the vaccine is twice vaccinated, it is only 60% effective.

Other research It has also been explored whether the combination of one dose of Johnson & Johnson vaccine and one dose of mRNA vaccine is more effective than two doses of Johnson & Johnson vaccine.