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Breakthrough SARS-CoV-2 Infection Following COVID-19 Vaccination in Patients with Cancer

Patients with cancer who develop breakthrough COVID-19 remain at risk of severe outcomes despite full vaccination
12 Jan 2022
Cancer in Special Situations / Population;  Haematologic malignancies

Researchers from the COVID-19 and Cancer Consortium point out in an article published on 24 December 2021 in the Annals of Oncology that patients with cancer who develop breakthrough COVID-19 following full vaccination remain susceptible to severe outcomes. Haematologic malignancies are over-represented among vaccinated patients with cancer who develop breakthrough COVID-19. Vaccination of close contacts, masking, boosters, and social distancing are needed to protect patients with cancer according to Dr Toni K. Choueiri of the Department of Medical Oncology, Dana-Farber Cancer Institute in Boston, MA, US and colleagues.

Using data from the multi-institutional COVID-19 and Cancer Consortium registry, the study team reported the clinical attributes of patients with cancer who develop breakthrough SARS-CoV-2 infections and compared their outcomes with those seen in a contemporary unvaccinated population.

This large international registry captures data on patients with a current or prior history of cancer who develop COVID-19. Deidentified data are collected using a comprehensive set of variables related to demographics, cancer status, anticancer therapies, SARS-CoV-2 infection, and COVID-19 vaccination. Data on COVID-19 vaccination were routinely collected on every new entered case.

Eligible cases included adult patients accrued from 1 November 2020 to 31 May 2021 with current or prior history of invasive cancer and laboratory-confirmed SARS-CoV-2 infection. Patients were excluded if vaccination status or timing was unknown or if the vaccine was administered after SARS-CoV-2 infection.

The study primary endpoint was 30-day all-cause mortality among fully vaccinated patients compared with the unvaccinated population after Inverse Probability of Treatment Weighting (IPTW) to adjust for baseline clinical variables. Secondary endpoints included rates of intensive care unit (ICU) admission and/or mechanical ventilation (MV), and hospitalisation rates in fully vaccinated, compared with unvaccinated patients after IPTW to adjust for baseline clinical variables.

Patients were categorised as fully vaccinated at the time of COVID-19 when two doses of vaccine had been administered and diagnosis of COVID-19 was recorded >4 weeks from first dose of BNT162b2, or when two doses of vaccine had been administered and a diagnosis of COVID-19 was recorded >6 weeks from the first dose of mRNA-1273, or in the event of a single dose of vaccination and a positive diagnosis >28 days post-vaccine in case of Ad.26.COV2.S. Patients who received at least one dose of vaccine and developed COVID-19, but did not meet the previous criteria were considered partially vaccinated.

IPTW was used to adjust for differences in baseline clinical variables between fully vaccinated and unvaccinated patients using age, biologic sex, race, smoking status, Eastern Cooperative Oncology Group performance status (ECOG PS), baseline corticosteroid use, lymphopenia, modified Charlson comorbidity index, cancer status, cancer type, and recent systemic anticancer therapy.

Of 1787 patients with cancer and COVID-19 who met inclusion criteria, 1656 (97%) were unvaccinated, 77 (4%) partially vaccinated, and 54 (3%) fully vaccinated. Median age of fully vaccinated patients was 65.5 years, 35 (65%) were female and 38 (70%) were non-Hispanic White. A total of 19 (35%) had haematologic malignancies and 17 (31%) had a modified Charlson comorbidity index of ≥2.

Before IPTW was carried out, more patients in the fully vaccinated cohort relative to the unvaccinated cohort had an underlying haematologic malignancy (35% versus 20%), were female (65% versus 55%), non-Hispanic White (70% versus 60%), received baseline prednisone or equivalent >10 mg/day (17% versus 7%), had absolute lymphocyte count <1000/μl (46% versus 28%), or received systemic therapy within the prior 3 months (56% versus 43%).

Among the 54 fully vaccinated patients who developed COVID-19, 35 (65%) were hospitalised, 10 (19%) were admitted to ICU or required MV, and 7 (13%) died within 30 days. Comparable rates were observed in the unvaccinated group.

Following IPTW there was no statistical difference in 30-day mortality between the fully vaccinated patients compared with the unvaccinated cohort with adjusted odds ratio (AOR) 1.08 (95% confidence interval [CI] 0.41-2.82). Increased 30-day mortality was associated with lymphopenia, the presence of comorbid conditions, worse PS, and baseline cancer status.

There were no significant differences in ICU/MV or hospitalisation rates between the vaccinated patients compared with the unvaccinated cohort after adjustment (AOR 1.13, 95% CI 0.54-2.37 and AOR 1.25, 95% CI 0.68-2.30). In both vaccinated and unvaccinated patients, higher ICU/MV and hospitalisation rates were identified in patients with lymphopenia, the presence of comorbid conditions, poor ECOG PS, and haematologic as opposed to solid malignancies.

The authors commented that it is the first study to evaluate the clinical characteristics and outcomes of patients with cancer who experience breakthrough infection following COVID-19 vaccination. 

Reference

Schmidt AL, Labaki C, Hsu C-Y, et al. COVID-19 vaccination and breakthrough infections in patients with cancer. Annals of Oncology; Published online 24 December 2021. DOI: https://doi.org/10.1016/j.annonc.2021.12.006

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