• immunisation
• general paediatrics

We read with interest recently published articles regarding fever post-immunisation following the introduction of the four-component meningococcal B vaccine (4CMenB).1–3

In retrospective1 and prospective2 audits, Nainani et al (n=38) and Kapur et al (n=35) demonstrated significant increases in emergency department (ED) attendances (0.8% of the local vaccinated population2), investigations (venepuncture in 38%1 and 62%,2 lumbar puncture (LP) in 22%1 and 17%2) and hospitalisations (72%1 and 51%2 (for post-immunisation fever). Murdoch et al’s3 self-controlled case series estimated an additional 1440 hospital admissions per year in the UK following 4CMenB introduction.

We conducted a retrospective audit of infants presented to the ED at the Royal Hospital for Sick Children, Edinburgh with post-immunisation fever between March and October 2016. Infants who presented with reported fever at home were included even if afebrile in ED. Forty-three infants were identified, aged 6–36 weeks. The mean temperature at presentation was 38.1°C (36.6°C–39.7°C). Thirty-seven per cent (16/43) had isolated fever, others had additional symptoms including irritability, poor feeding and vomiting. Eighty-one per cent of the infants presented following their 2-month and 4-month immunisations (coinciding with 4CMenB vaccination).

In our cohort, 67% of infants were discharged from ED, the majority without investigations. Fourteen (33%) were admitted and had blood taken for inflammatory markers, and blood and urine for culture. Seven (16%) also had LPs and received intravenous antibiotics. All cerebrospinal fluid (CSF) and blood cultures were negative; one urine culture was positive for Escherichia coli and one CSF positive for Enterovirus. The results of the investigations are summarised in table 1. The mean length of stay was 2.1 days (range 1–5).

We have considered our results in the context of the current ‘Fever in under 5 s’ National Institute for Health and Care Excellence guidance (CG160).4 This advises that feverish infants under 3 months of age should have blood tests (FBC, CRP, culture) and urine culture performed. Feverish infants over 3 months should have investigations if unwell. LPs are recommended if WCC is <5 or >15×10⁹/L. According to this guidance, at least half of our infants should have had LPs, including some who were discharged.

In our cohort, infants under 3 months of age were more likely to be admitted and have invasive investigations than older infants (table 2).

Recent evidence has demonstrated an increase in ED presentations and hospitalisations with post-immunisation fever following the introduction of 4CMenB. Current guidance does not account for this presentation, and published literature suggests variable clinical management of cases. Of all cases reported in Nainani et al, Kapur et al and our audits (116 patients in total), only one potentially significant bacterial infection was identified.

Additional data are required to update guidance around investigation and management of post-immunisation fever following 4CMenB introduction. Increased emphasis to families of the importance of routine paracetamol use before and after 4CMenB vaccination in infants may help reduce these presentations.