Long-term 4CMenB Vaccine Effectiveness Against Gonococcal Infection at Four Years Post-Program Implementation: Observational Case-Control Study.

BACKGROUND

A 4-component meningococcal B (4CMenB) vaccine program was introduced in adolescents in 2019 in South Australia. We aimed to evaluate long-term vaccine effectiveness (VE) and impact (VI) on gonococcal infection 4 years after implementation of the program.

METHODS

Disease notification data were provided by SA Health. VE was estimated as the reduction in the odds of infection using the screening and case-control methods. Time-to-event analyses assessed vaccine effect on reinfections. VI was estimated as incidence rate ratios (IRRs) using negative binomial regression models.

RESULTS

At 4 years after implementation of the program, 2-dose VE against gonococcal infection was 44.3% (95% CI, 35.1%-52.2%) using chlamydia patients as controls. Lower VE estimates were demonstrated in those >48 months post-4CMenB vaccination (26.2%; 95% CI, -2.6% to 47.0%) compared with those who had been vaccinated within ≤48 months (46.0%; 95% CI, 36.3%-54.2%). Slightly higher VE estimates were observed in females (48.7%; 95% CI, 36.9%-58.2%) compared with males (38.0%; 95% CI, 22.0%-50.7%). The risk of a second episode of gonococcal infection was lower in vaccinated gonococcal cases (adjusted hazard ratio, 0.682; 95% CI, 0.450-1.034). The adjusted IRR was 0.635 (95% CI, 0.421-0.957), with an observed 36.5% reduction in gonococcal infection.

CONCLUSIONS

4CMenB demonstrates moderate effectiveness against gonococcal infection, with a lower VE estimate after 4 years postvaccination. 4CMenB may reduce the risk of recurrent gonococcal infection. The requirement for a booster dose and dosing interval warrants evaluation.