A meningococcal immunisation programme specifically targeting adolescent carriers rapidly controlled a national outbreak of meningococcal group W (MenW), UK data shows.
The UK started an emergency adolescent immunisation programme in 2015 with the meningococcal ACWY conjugate vaccine to combat a national outbreak of MenW disease sparked by a hypervirulent ST-11 complex strain, researchers reported in the Lancet Child and Adolescent Health.
‘This immunisation programme specifically targeted adolescents aged 13-18 years, an age group with low disease incidence but high nasopharyngeal carriage, with the aim of interrupting transmission and providing indirect (herd) protection across the population,’ the authors said.
Reporting the impact of the first four years of the program in England, the Public Health England-funded study found MenW and MenY cases plateaued within 12 months and then declined, while Men C cases remained low throughout.
For MenW, based on conservative and extreme scenarios, 205-1193 MenW cases were prevented through the indirect effects of the programme and 25 through direct protection, researchers said.
For MenY, an estimated 60-106 cases were prevented through indirect effects and 19 through direct protection.
‘Ignoring any residual effect from an earlier MenC-containing vaccine, the overall effectiveness against MenCWY disease combined was 94%,’ the researchers concluded.
They noted vaccine uptake, as evaluated in August 2019, was 37-41% in adolescents immunised in primary care and 71-86% in younger teenagers routinely vaccinated in schools.
‘After replacing the routine school-based MenC conjugate vaccine with the MenACWY vaccine for adolescents aged 13-14 years, priority was given to those aged 18 years (ie, school leavers) and new university entrants because the latter group had a significantly higher risk of invasive meningococcal disease than their peers who did not attend university,’ the study authors noted.
Within 12 months of the programme, the trend in increasing MenW cases stopped accelerating, with marked declines among school leavers attributed to a direct effect of the program, despite only 36.6% uptake among this cohort.
‘Overall, MenW cases continued to decline in subsequent years as more adolescent cohorts were immunised, with the greatest decline observed during 2018-2019 when the first cohort of adolescents immunised as part of the school-based programme, with 77.2% vaccine uptake, entered university,’ the study authors wrote.
An accompanying editorial noted that it was impossible to know whether cases would have declined anyway even without the vaccination programme as had been observed in other outbreaks, but said despite this limitation the study would be useful to understand the impact of the UK’s national vaccination programme and may inform vaccine policy for other countries facing similar outbreaks.