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December 07, 2021

Matching a J&J booster with the Pfizer vaccine prompts a robust immune response, study finds

The combination better sustains antibody levels than a third Pfizer dose

Prevention COVID-19
Johnson & Johnson booster Vickie Connor/The Desert Sun

People who receive a Johnson & Johnson booster shot after initially receiving the Pfizer COVID-19 vaccine have a slow, but sustained immune response against the coronavirus, including most variants, a new study found.

Researchers have been exploring a mix-and-match approach to COVID-19 boosters as the pandemic shows no sign of ending. 

Allowing people to receive a booster shot that differs from their initial vaccine regimen makes widespread boosting easier. But the combinations may not be equally effective. 

People who receive the Johnson & Johnson vaccine as a booster after initially receiving the two-dose Pfizer-BioNTech vaccine have a slower, but sustained immune response against the coronavirus, including most variants, a new study found. The analysis didn't include the omicron variant.

By contrast, receiving a third Pfizer-BioNTech dose elicited a quicker immune response, but it petered out faster. 

Both vaccines boosted antibodies well, but after four weeks the antibody levels of volunteers who received a Pfizer booster shot began to decrease significantly, researcher Dr. Dan Barouch, of Beth Israel Deaconess Medical Center in Boston, told CNN.

The antibody levels of volunteers who received the J&J booster continued to climb after four weeks. The J&J booster also triggered an increase in T cells, a second line of defense against infection. T cells won't stop an infection from occurring, but they can prevent it from progressing to a severe illness. 

The boost in T cells may be particular helpful for fighting variants that may partially evade antibodies, Barouch said.

The small study, which included 65 volunteers, is posted online on the preprint server MedRxiv. The researchers also submitted their findings to a peer-reviewed journal.

An earlier National Institutes of Health study found that people who initially received the Johnson & Johnson vaccine produced a stronger antibody response after receiving a Moderna or Pfizer booster. Receiving a second J&J shot boosted antibody levels fivefold. But a Moderna booster triggered antibody levels more than 50 times higher.

That study also found that people who first received the Pfizer or Moderna vaccines and later received the other as a booster dose also had strong immune responses.

However, that study wasn't designed to determine if certain combinations were more effective than the others. Its purpose was to show that vaccines can safely be used interchangeably.

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