People with haematological cancers show poor immune responses after a single dose of Pfizer’s COVID-19 vaccine, highlighting the need for patients to receive the second dose as soon as possible, researchers say.
A prospective study involving 151 cancer patients in the UK found that three weeks following the first dose of mRNA-based SARS-CoV-2 BNT162b2 vaccine immunogenicity was 18% in those with haematological cancers, 38% in patients with solid cancers and 98% in a control group of healthy people after the first dose of the vaccine.
Seroconversion rates were better after the second dose of vaccine given at 21 days after the first, with 60% of those with haematological cancer showing immunogenicity, compared to 95% of patients with solid cancer and 100% of the healthy control group.
Published in Lancet Oncology, the results showed that vaccine responses remained poor for people who had only a single dose, and the low serological conversion rates were accompanied by low viral neutralisation capacity and T-cell responses at five weeks.
Researchers from the Francis Crick Institute and King’s College London said the apparently low vaccine efficacy seen in patients with haematological cancers would need to be confirmed in larger studies because of the low numbers of patients who received a second dose.
Nevertheless, they said the overall results confirmed previous findings of low vaccine efficacy for patients with cancer receiving seasonal vaccines, “and imply that single-dose BNT162b2 vaccination leaves most patients with cancer wholly or partially immunologically unprotected.”
“The poor immune efficacy of single-dose BNT162b2 vaccination in patients with cancer observed in this study is abundantly clear, as is the profound positive effect of day 21 boosting in patients collectively reflecting a wide range of solid cancers and treatments,” they wrote.
They added that the vaccine was safe and well tolerated in patients with cancer, and the responses to a second dose were seen across a range of cancers. They also noted that 47% of those with haematological cancers and 41% of patients with solid cancers had received anticancer treatment within 15 days of their initial dose of vaccine.
“The prospect that patients with cancer might be wholly or partially unprotected by vaccination has implications for their health and for the control of SARS-CoV-2 transmission within their environments, including health-care facilities,” they said.
“Our data support prioritisation of patients with cancer for an early (day 21) second dose of the BNT162b2 vaccine. Given the globally poor responses to vaccination in patients with haematological cancers, post-vaccination serological testing and careful follow-up should be prioritised for these patients, together with vaccination of those in close contact with them, in order to promote herd immunity.”
In Australia, cancer patients are being offered COVID-19 vaccine as a priority in the Phase 1b of the rollout, though the official advice does not specify whether patients should receive any specific vaccine.
The advice from Cancer Australia is that the two doses of the Pfizer/BioNTech vaccine should be given at least three weeks apart.
“It is particularly important for people with cancer to get the second dose of the vaccine as close to three weeks after the first dose as possible to ensure they are adequately protected from COVID-19,” it said.