medwireNews: The booster dose of the Pfizer–BioNTech COVID-19 vaccine should not be delayed in people with cancer, suggest the results of two studies showing insufficient immunogenicity with just the first dose.
“Our data support prioritisation of patients with cancer for an early (day 21) second dose of the BNT162b2 vaccine,” say the authors of the UK study, while the authors of the French study additionally highlight the need for cancer patients “to maintain strict social protection measures for at least 6-8 weeks after the first dose of the vaccine.”
The interim analysis of the SOAP-02 vaccine study was published in The Lancet Oncology and included 151 patients with cancer (solid cancer in 95, hematologic in 56) and 54 cancer-free controls (primarily healthcare workers) who received one or two 30 μg doses of the Pfizer–BioNTech (BNT162b2) vaccine between December 2020 and February 2021 at one of three centers in London, UK.
Among participants with available blood samples, the rates of seroconversion to the SARS-CoV-2 spike (S) protein at 3 weeks after the first vaccine dose were 38% in the solid cancer cohort (n=56), 18% in the hematologic cancer cohort (n=44), and 94% in the control group (n=34).
Noting that median anti-S antibody titers “were largely similar in each cohort,” the researchers say that “the main difference between healthy controls and patients with cancer was a failure to produce a response, rather than the magnitude of the response.”
They then assessed the impact of the second vaccine dose, given 21 days after the first one, and found that 95% of the 19 solid cancer patients who received the booster dose had anti-S seroconversion at the 5-week timepoint. This was significantly higher than the rate of 30% among the 33 who did not receive the booster due to changes in national government guidelines.
Similarly, the seroconversion rate was higher for the five patients with hematologic cancer who received the boost than for their 36 counterparts who did not, at 60% and 11%, respectively, but the team notes that this comparison was “insufficiently powered” for clinical interpretation.
The rates for the 12 control participants who received the boost and the 21 who did not were 100% and 86%, respectively.
These findings “imply that single-dose BNT162b2 vaccination leaves most patients with cancer wholly or partially immunologically unprotected,” and therefore “a case could be made to reassess current UK policy of a 12-week BNT162b2 dosing interval in patients with cancer and other high-risk groups,” conclude Sheeba Irshad (King’s College London) and colleagues.
The second study – by Jérôme Barrière (Clinique Saint Jean, Cagnes-sur-Mer, France) and co-workers – comprised 122 patients with solid tumors and 29 cancer-free controls who received the BNT162b2 vaccine between January and March 2021. The majority (86%) of cancer patients were receiving chemotherapy, with or without targeted therapy.
At the first assessment, conducted 3–4 weeks after the first vaccine dose, 47.5% of evaluable patients achieved anti-S seroconversion, increasing to 95.2% of patients at the second assessment, at 3–4 weeks after the booster dose. This compared with an anti-S seroconversion rate of 100% among the assessable healthy controls at both the first and second assessment.
Of note, the seroconversion rate was significantly lower among patients receiving chemotherapy than those who were not or were receiving targeted therapy alone, at 42.9% and 76.5%, respectively.
As reported in a letter to the Annals of Oncology, median anti-S antibody titers were significantly lower among cancer patients than controls at the first and second assessments, at 0.52 versus 21.6 IU/mL and 245.2 versus 2517.0 IU/mL, respectively. But the investigators note that median titers “increased significantly” for both groups after the booster dose.
And they conclude: “The duration of immunity acquired under chemotherapy as well as the level of protection against the different SARS-CoV-2 variants are unknown. As already shown for flu vaccine, efficacy of a second booster dose (third dose) has to be studied.”
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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Lancet Oncol 2021; doi:10.1016/S1470-2045(21)00213-8
Ann Oncol 2021; doi:10.1016/j.annonc.2021.04.019