medwireNews: A small phase 1 trial suggests that a third booster dose of the Pfizer–BioNTech (BNT162b2) vaccine in patients receiving anticancer therapy could improve their immunologic response to SARS-CoV-2.
“[O]ur data suggest that most patients with cancer on active chemotherapy are likely to exhibit improved antibody levels, which has been correlated with protection against disease, after a third immunization,” write the investigators in Nature Medicine.
“However, given the relatively modest increases in antibodies and recalcitrance of T cells, expectations should remain tempered as to the degree of benefit,” they caution, and add: “Quantitative antibody tests can potentially be used to select individuals who need, and would most benefit from, a booster.”
The study included 20 patients – 15 with gastrointestinal cancers and five with breast cancer – who were receiving systemic cytotoxic therapy, most commonly gemcitabine-based regimens (50%). Participants were aged a mean of 63.1 years, two-thirds were women, and all had received two doses of the Pfizer–BioNTech vaccine.
Rachna Shroff and colleagues from the University of Arizona in Tucson, USA, analyzed blood samples drawn 1 week after the third vaccine dose – given 47–122 days after the second dose – and found a “modest but consistent and statistically significant” rise in mean titers of antibodies against the SARS-CoV-2 spike protein relative to levels at the time of vaccine administration, at 0.72 and 0.49, respectively.
The team also observed a significant increase in titers of virus-neutralizing antibodies after versus before the booster, at a median 90% plaque reduction neutralization test titer of 180 versus 60, but there was no increase in T-cell levels.
Of note, the researchers did not find any correlation between the time between vaccine doses and either the spike-specific or neutralizing antibody response, but they draw attention to the small number of patients in the study.
There were no serious adverse events (AEs) at either 2 weeks or 4 weeks after the administration of the booster dose. The most common AE was injection site pain, reported by 45% of participants, followed by myalgia in 15%, fatigue and chills each in 10%, and appetite loss and bone pain each in 5%.
medwireNews is an independent medical news service provided by Springer Healthcare Ltd. © 2021 Springer Healthcare Ltd, part of the Springer Nature Group
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