286P - Breakthrough COVID-19 infections in patients with cancer from a prospective study of COVID-19 vaccine response

Background

COVID-19 disease is more severe in unvaccinated cancer patients compared with the general population. There is limited data regarding clinical efficacy of vaccination in these patients.

Methods

SerOzNET (ACTRN12621001004853) is a prospective observational cohort study of adults and children with cancer receiving COVID-19 vaccination. The primary endpoint is serological response. An important secondary endpoint is outcome of COVID-19 infection after vaccination. We report self- and clinician reported COVID-19 infections.

Results

Of 395 adults (20 years +), 74 (19%) reported COVID-19 infection over mean duration on study of 259 days. 71 (97%) had received 2 vaccine doses, 51 (69%) received 3+ doses. 21 (28%) had antiviral treatment. 62 (84%) had symptoms, 7 (9%) required hospitalisation, 0 required ICU admission or died due to COVID-19. Of 113 children/adolescents (5-19 years), 31 (27%) reported COVID-19 infection over mean duration on study of 215 days. 28 (90%) had received 2 vaccination doses, and 12 (39%) received 3+ doses. 23 (74%) had symptoms, 8 (25%) required hospitalisation, 2 (6%) had antiviral therapy, 0 required ICU admission or died due to COVID-19. Pediatric pts with COVID-19 infection had increased risk of hospitalisation compared with adults (p=0.03). Hematological cancer pts had non-significant but numerically higher rates of hospitalisation (Table). Table: 286P

*Diagnosis data unavailable for 2 adults and 10 children

Conclusions

Pts with cancer are likely to be exposed to COVID-19, with infection rates similar to the wider population. Vaccination appears to protect against ICU admission in cancer patients. However, 9% of adults and 25% of children with cancer required hospitalisation for COVID-19, demonstrating increased severity of symptoms compared to the general population. Higher rates of infection and hospitalisation in pediatric pts may be partly attributable to the lower proportion of children who had received a 3^rd vaccination dose at the time of infection.

Clinical trial identification

ACTRN12621001004853.

Editorial acknowledgement

Legal entity responsible for the study

Monash Health.

Funding

Cancer Australia (Australian Federal Government) Victorian Cancer Agency (Victorian State Government, Australia) Leukaemia Foundation (Foundation, Australia).

Disclosure

All authors have declared no conflicts of interest.