NEW YORK (Reuters Health) – For patients with blood cancer, three doses of COVID-19 vaccine may not generate detectable neutralizing antibodies against the Omicron variant of SARS-CoV-2, which has rapidly become the dominant variant worldwide, according to a new study from the UK.

Omicron is known to partially evade vaccine-induced immunity. A third vaccine dose has been shown to boost Omicron neutralizing antibody (nAb) responses in the general population, but comparable data in patients with cancer are lacking.

To investigate, Dr. Samra Turajlic with the Francis Crick Institute in London and colleagues studied 115 patients with solid cancer and 84 with blood cancer, all of whom had received a third dose of the Pfizer COVID-19 vaccine after two doses of either the Pfizer vaccine or the AstraZeneca vaccine.

They found that 90% of patients with solid cancer had detectable nAb titers against Omicron after the third vaccine dose, compared with only 56% of the patients with blood cancer.

In a letter to the editor in The Lancet, they say “only a few” patients with solid cancer lacked nAb titers against Omicron after three vaccine doses, whereas a “substantial proportion” of patients with blood cancer, especially those on B-cell-depleting therapies or with progressive cancer, did not mount a detectable response.

“The incremental benefit of a third vaccine dose in boosting nAb responses in patients with blood cancer lends support for a fourth dose in this population, as per UK guidance at the time of writing,” the authors conclude.

SOURCE: https://bit.ly/3rcqzG2 The Lancet, online January 25, 2022.

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