Laboratory reports of Haemophilus influenzae by age group and serotype, England: annual 2022 (and 2021)
Updated 15 August 2023
Applies to England
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During 2022 (January to December inclusive), there were 608 confirmed cases of invasive Haemophilus influenzae (Hi). This was a 57% increase compared to 2021 (608 in 2022 compared with 387 in 2021) (Table 1).
Restrictions due to the COVID-19 pandemic were associated with reductions in a number of infections, including invasive Haemophilus influenzae disease, during 2020 (1), with cases remaining low during 2021 and since rebounding in 2022.
In 2022, 12.3% (75 of 608) were not serotyped, compared to 11.1% (43 of 387) not typed in 2021. Of those serotyped, most isolates were non-encapsulated Haemophilus influenzae (ncHi) (80.5%; 429 of 533), which is slightly higher than the proportion of ncHi in 2021 (76.5%; 263 of 344).
In 2022 and 2021, there were 7 cases of invasive H. influenzae serotype b (Hib) disease, accounting for 1.3% (7 of 533) and 2.0% (7 of 344), respectively.
In 2022, all Hib cases were identified in persons over the age of 15, while 2 of the cases in 2021 were in children under the age of 5 years.
Other serotypes causing invasive disease in 2022 (18.2%) included:
- 57 serotype f
- 20 serotype a
- 20 serotype e
In 2021, other serotypes accounted for 21.5% of all cases due to a slightly lower number of ncHi cases (Table 1).
Most invasive H. influenzae infections (83.4%) in 2022 were in adults aged 15 years and over (Table 1), similar to 2021 (83.2%). This was followed by cases in infants aged less than 1 year, which accounted for 8.4% (n=51) of cases in 2022 compared to 5.7% (n=22) in 2021. While there was a slight increase in the number of cases in the 1 to 4 and the 5 to 14 years age groups (Table 1) from 2021 to 2022, the proportion of cases in those aged 1 to 4 years of age has slightly decreased (7.2% to 4.8% from 2021 to 2022).
The incidence of invasive H. infuenzae due to any serotype remains higher in children aged under 5 years (2.6 per 100,000 population), compared to those aged 5 years and older (1.0 per 100,000 population) but overall the total incidence remains very low (1.1 per 100,000 population in 2022 and 0.7 per 100,000 in 2021).
There were no deaths attributed to invasive Hib disease in 2022 and 2021. The most recent deaths attributed to invasive Hib disease were in 2015, in an adult, and in 2011, in a child.
As reported previously [2], cases of invasive Hib disease have declined since the introduction of the Hib conjugate vaccine in 1992 and have remained at low levels since the introduction of the 12-month booster in 2006 (Figure 1). In 2022, invasive Hib disease continued to be well controlled across all age groups.
Table 1. Number of Haemophilus influenzae cases by serotype and age group, England, 2020 and 2021.
(‘Not typed’ refers to samples that have not been received at the reference laboratory for typing.)
| Type | <1 year: 2021 | <1 year: 2022 | 1 to 4 years: 2021 | 1 to 4 years: 2022 | 5 to 14 years: 2021 | 5 to 14 years: 2022 | 15+ years: 2021 | 15+ years: 2022 | Total 2021 | Total 2022 |
|---|---|---|---|---|---|---|---|---|---|---|
| b | 1 | 0 | 1 | 0 | 0 | 0 | 5 | 7 | 7 | 7 |
| Non capsulated | 14 | 36 | 17 | 21 | 10 | 14 | 222 | 358 | 263 | 429 |
| a,e,f | 4 | 6 | 10 | 5 | 4 | 4 | 56 | 82 | 74 | 97 |
| Not typed | 3 | 9 | 0 | 4 | 1 | 2 | 39 | 65 | 43 | 75 |
| Total | 22 | 51 | 28 | 29 | 15 | 20 | 322 | 508 | 387 | 608 |
Figure 1. Total cases of Haemophilus influenzae by year, 2000 to 2022
References
1. Brueggemann AB, Jansen van Rensburg MJ, Shaw D, McCarthy ND, Jolley KA, Maiden MCJ, and others (2021). Changes in the incidence of invasive disease due to Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis during the COVID-19 pandemic in 26 countries and territories in the Invasive Respiratory Infection Surveillance Initiative: a prospective analysis of surveillance data. The Lancet Digital Health: volume 3, issue 6
2. Laboratory reports of Haemophilus influenzae by age group and serotype (England and Wales): annual report for 2015. Health Protection Report: volume 10 issue 8