Research and analysis

HPR volume 9 issue 30: news (28 August)

Updated 29 December 2015

1. Laboratory confirmed pertussis in England: data to end-June 2015

This report presents current pertussis activity to 30 June 2015, updating the previous report that included data to the end of February 2015 [1].

1.1 Background

In England the number of laboratory confirmed cases of pertussis has fallen overall each consecutive year from a peak of 9,367 cases in 2012; by 51% between 2012 and 2013 (4,621 cases) and 27% between 2013 and 2014 (3,388 cases). A seasonal increase is usually observed from the second and into the third quarter of the year and activity increased as expected in May and June 2015. The 1744 laboratory confirmed cases reported in 2015 to the end of June (provisional data) was lower than the same period in 2012 (2399 cases) and 2013 (2745 cases) but higher than the same period last year (1412 cases). Overall pertussis activity in England persists at raised levels compared to the years preceding the outbreak in 2012*.

The pertussis vaccination in pregnancy programme was introduced in October 2012 [2,3] in response to a national outbreak and is offered to women ideally between 28-32 weeks pregnancy to protect infants in their first few weeks of life. Confirmed pertussis cases in infants <6 months of age have remained low despite the continued high activity in other age groups**. The immunisation programme for pregnant women continues to be important, particularly in light of the ongoing raised levels of pertussis in those from 1 year of age and recent infant deaths. There have been recent key publications on the high effectiveness and safety of the pertussis immunisation in pregnancy programme [4,5,6]. Together with coverage and epidemiological data, these findings informed the Joint Committee on Vaccination and Immunisation’s (JCVI) decision in July 2014 that the pregnancy programme should continue for at least a further 5 years [7].

The latest pertussis vaccine coverage estimates [8] in pregnant woman in England indicate that coverage decreased from 59.3% in January to 55.2% in May 2015. This decline followed a similar seasonal pattern to that observed in 2013 and 2014 with coverage dropping in the first quarter and starting to plateau at the end of spring, although the decline has been less pronounced in 2015, with coverage at 55.2% in May 2015 compared to 50% and 53.6% in the same month in 2013 and 2014 respectively.

1.2 Confirmed cases in 2015

In infants under 3 months of age low numbers of cases have been sustained since December 2012. Pertussis activity in all infants <1 year of age was was low in the first 6 months of 2015, with 65 cases, but higher than the equivalent period in 2014 (49 cases)**; disease incidence, as expected, continued to be highest in this age group but case reports are now in line with those seen before the 2012 peak, when there were 222 cases in the first 6 months of the year. There have been 2 deaths in infants with pertussis confirmed this year.

The numbers of laboratory confirmed cases in those aged 1 year and older, however, continued to be higher than those reported before the 2012 outbreak. Pertussis cases in those aged 10 years and older were lower in the first 6 months of 2015 than the totals confirmed in 2012. In those aged 1-9 years however cases to 30th June 2015 (31 aged 1-4 years and 87 aged 5-9 years) are nearly double those confirmed to the same point in 2012 (16 cases aged 1-4 years and 49 cases aged 5-9 years), although a similar number were reported in those aged 1-4 years in 2013 (28 cases). Overall confirmed pertussis cases were higher to end June 2015 than in the comparable period in 2014.

1.3 Overall trends as at end-June 2015

The greatest reduction in disease since the peak in 2012 has been in infants aged under 6 months. Overall pertussis activity was relatively high in the first 6 months of 2015 in all Regions of the country***, in particular in children aged 1-9 years. Twelve deaths have been reported in young babies with confirmed pertussis who were born after the introduction of the pregnancy programme on 1 October 2012, as at end June 2015. Eleven of these 12 babies were born to mothers who had not been vaccinated against pertussis, all of the 12 babies were too young to be fully protected by vaccination themselves and only one had received their first dose of pertussis-containing vaccine.

* See figure in the PDF version of this issue of HPR.

** See table 1 in the PDF version of this issue of HPR.

*** See table 2 in the PDF version of this issue of HPR.

1.4 References

1. Laboratory confirmed pertussis in England: data to end-February 2015. HPR 9(17): news (15 May 2015).
2. “Pregnant women to be offered whooping cough vaccination”, 28 September 2012. Department of Health website.
3. “HPA welcomes introduction of whooping cough vaccination for pregnant women as outbreak continues” HPA press release, 28 September 2012.
4. Amirthalingam G, Andrews N, Campbell H et al (2014). Effectiveness of maternal pertussis vaccination in England: an observational study Lancet.
5. Donegan K, King B, Bryan P (2014). Safety of pertussis vaccination in pregnant women in the UK: observational study British Medical Journal.
6. Dabrera G, Amirthalingam G, Andrews N et al (2014).A case-control study to estimate the effectiveness of maternal pertussis vaccination in protecting newborn infants in England and Wales, 2012–2013 Clinical Infectious Diseases (online), 19 October.
7. JCVI minutes.
8. Pertussis Vaccination Programme for Pregnant Women: vaccine coverage estimates in England (PHE statistics).