Moderna Switch

After Pfizer shot better against omicrons in 60+

mix it up — The study is small but adds to data finding benefits of mix-and-match boosting. Beth Mole – May 13, 2022 9:55 pm UTC Enlarge / The Comirnaty (Pfizer/BioNTech) and Moderna COVID-19 vaccines.People ages 60 and older who were initially vaccinated with two Pfizer-BioNTech COVID-19 vaccine doses were better protected from the omicron…

, switch to Moderna booster
Mix it up

Although the study is limited, it adds to the data-finding benefits of mix-and match boosting.

The Comirnaty (Pfizer/BioNTech) and Moderna COVID-19 vaccines.

Enlarge / The Comirnaty (Pfizer/BioNTech) and Moderna COVID-19 vaccines.

People ages 60 and older who were initially vaccinated with two Pfizer-BioNTech COVID-19 vaccine doses were better protected from the omicron coronavirus variant after being boosted with a Moderna vaccine rather than another dose of the Pfizer-BioNTech vaccine.

Those results are according to interim data from a small but randomized controlled clinical trial in Singapore and published this week in the journal Clinical Infectious Diseases.

The study–involving 98 healthy adults–can’t determine if the Moderna booster is simply superior to a Pfizer-BioNTech booster for older adults or if a mix-and-match booster strategy is inherently better. The study also only focused on antibody levels. This may or may not have translated into significant differences in infection rates or other clinical differences. It also only followed people for 28 days after a booster, so it’s unclear if the Moderna booster’s edge will hold up over time.

Still, the authors of the study, led by Barnaby Young of Singapore’s National Centre for Infectious Diseases, report that the beneficial effect seen by swapping from Pfizer-BioNTech to Moderna was significant enough that they don’t expect it to vanish with more participants. It also follows other studies that have suggested that mix-and-match boosting–aka heterologous boosting–can generate slightly different antibodies and reduce the incidence of SARS-CoV-2 infections in people 60 and older.

For the new study, Young and colleagues looked at antibody levels in adults of all ages who had received two Pfizer-BioNTech COVID-19 vaccine doses between six and nine months before receiving a booster dose. People who had a compromised immune system or were suspected of having had an anti-N antibody-producing infection (SARS-CoV-2) prior to the start of the trial were excluded.

Of the 98 participants, 50 went on to get another Pfizer-BioNTech vaccine dose for their booster (homologous booster), while the remaining 48 received a Moderna booster (heterologous booster). The authors looked at their resulting antibody responses on the day of their booster, seven days later, and 28 days later. They compared the total antibodies that attacked the receptor binding domain, a key component of the SARS-2 spike protein. They also compared levels of neutralizing antibodies against specific SARS-CoV-2 variants. This included the ancestral strain, alpha, beta and delta, as well as omicron.

Slightly bigger boost

Overall, the heterologous-boosted group had slightly higher total antibody levels than the homologous group–about 40 percent higher on day seven and 30 percent higher on day 28, though the confidence intervals overlapped.

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