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
13 October 2021: The coronavirus pandemic is affecting all healthcare professionals across the globe. Medicine Matters’ focus, in this difficult time, is the dissemination of the latest data to support you in your research and clinical practice, based on the scientific literature. We will update the information we provide on the site, as the data are published. However, please refer to your own professional and governmental guidelines for the latest guidance in your own country.
Nat Med 2021; doi:10.1038/s41591-021-01542-z