Patients with CLL benefit from a personalised COVID-19 vaccination strategy based on attaining adequate anti-spike levels (≥5,000 AU/mL), Australian research shows.

The study, published in the British Journal of Haematology [link here], said high anti-spike levels provide protection against infection, as well as decreasing the risk of severe COVID-19, hospitalisation and death.

The Sydney study reported on 241 CLL and 55 monoclonal B-lymphocytosis (MBL) patients following multiple vaccine doses aiming for maximum measured anti-spike antibody response. Patients had between three and eight vaccine doses from March 2021.

It found 53.9% of CLL patients and 40.0% of MBL patients contracted PCR- or RAT-documented COVID-19. Seven CLL patients had a second COVID-19 infection.

The hospitalisation rate was 6.2% in CLL with one death recorded. There were no hospitalisations or deaths in the MBL group. Anti-viral therapies were used in 47.3% of CLL and 31.8% of MBL patients.

The study found median anti-spike levels in CLL patients who developed COVID-19 infection were significantly lower compared to those who did not develop COVID-19 (3,778.8 AU/mL v 13, 486.8 AU/mL; p = 0.0061), “suggesting a protective effective against contraction of COVID-19”.

However there was no similar association between anti-spike levels and COVID-19 infections in MBL patients.

“Higher anti-spike antibody responses are associated with neutralising antibody and T-cell responses that are likely important components of protection against severe COVID-19,” the study said.

“This remains highly relevant as contemporary Omicron strains such as XBB are resistant to prophylactic antibodies.”

The study found CLL patients with low anti-spike levels <5000 AU/mL had a higher risk of COVID-19 infection (relative risk = 1.73, p = 0.0003; and odds ratio = 3.92, p = 0.0005).

“While measuring vaccine antibody response for the general community is not recommended, this study suggests that in CLL it is important to identify patients who may benefit from additional vaccine doses, as attaining adequate anti-spike levels (≥5,000 AU/mL) results in very low mortality and hospitalisation rates and appears to be the predominant protective factor,” the study concluded.

“The small proportion unable to generate an endogenous response relies primarily on anti-viral therapy to mitigate severity.”

The investigators included senior investigator Professor Stephen Mulligan from the Royal North Shore Hospital in Sydney.