July 21, 2021 -- A new study says the one-dose Johnson & Johnson vaccine provides less protection against the Delta and Lambda variants than against the original COVID-19 strain.

The study, which was published online Monday at bioRxiv, said the J&J vaccine’s effectiveness in neutralizing those two variants was “significantly decreased” over time. (BioRxiv is a “preprint server” -- it posts the results of studies before they’ve been reviewed by other researchers and placed into medical journals.)

People vaccinated with the J&J vaccine may need to get a second shot, perhaps with the Moderna or Pfizer-BioNTech vaccines, to achieve good protection against variants, the study said.

"The message that we wanted to give was not that people shouldn’t get the J&J vaccine, but we hope that in the future, it will be boosted with either another dose of J&J or a boost with Pfizer or Moderna," Nathaniel Landau, PhD, a virologist at NYU’s Grossman School of Medicine who led the study, told The New York Times.

So far, federal health authorities are not recommending booster shots.

The findings of the new study are somewhat different from a J&J-sponsored study that found the J&J vaccine provides “strong, persistent” protection against the Delta variant.

Seema Kumar, a spokeswoman for J&J, told the Times that the findings of the new study “do not speak to the full nature of immune protection.” Studies sponsored by the company indicate that the vaccine “generated strong, persistent activity against the rapidly spreading Delta variant,” she said.

Meanwhile, another scientist told the Times the results of the new study are not surprising because all the COVID-19 vaccines seem to work better with two doses.

“I have always thought, and often said, that the J&J vaccine is a two-dose vaccine,” said John Moore, PhD, a virologist at Weill Cornell Medicine in New York City.

The Delta variant is now the dominant strain of COVID-19 in the United States, accounting for about 83% of new cases, CDC Director Rochelle Walensky, MD, told a Senate committee on Tuesday.

The Lambda variant, also known as C.37, was first identified in Peru in August 2020. It has spread throughout South America, and the World Health Organization designated it a “variant of interest” in mid-June.

The J&J vaccine is made using a type of virus called adenovirus type 26, or Ad26. The Ad26 delivers a piece of the DNA, or genetic material, used to make the spike protein, so the person can temporarily make this protein and teach the immune system to react against the coronavirus.

The two-shot vaccines from Pfizer and Moderna use a technique known as mRNA, or messenger RNA. These vaccines "give instructions for our cells to make a harmless piece of what is called the 'spike protein,'" according to the CDC. This protein is found on the surface of the coronavirus that causes COVID-19.

Show Sources

BioRxiv: “Comparison of Neutralizing Antibody Titers Elicited by mRNA and Adenoviral Vector Vaccine against SARS-CoV-2 Variants.”

The New York Times: “J.&J. Vaccine May Be Less Effective Against Delta, Study Suggests.”

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