Decline in invasive pneumococcal disease in Ireland since introducing the
7-valent pneumococcal conjugate vaccine (PCV7)
M. Fitzgerald1, I. Vickers2, P. O’Lorcain1, S. Murchan1, S. Cotter1, D. O’Flanagan1, M. Cafferkey2, H. Humphreys3,4
1Health
3Department
Protection Surveillance Centre, Dublin; 2Children’s University Hospital, Temple Street, Dublin;
of Clinical Microbiology, Royal College of Surgeons in Ireland; 4Department of Microbiology, Beaumont Hospital, Dublin.
KEY POINTS
Since the introduction of PCV7 in September 2008:
METHODS
¾ IPD infections due to PCV7 serotypes declined by 83% in children <2 years of age and
by 55% due to all serotypes in this age group
¾Irish microbiology laboratories submitted invasive Streptococcus pneumoniae isolates,
to the National IPD Typing Project for typing
¾ Serotype
S t
7F has
h replaced
l
d 14 as th
the mostt common serotype
t
associated
i t d with
ith IPD
Serotyping was performed using multiplex PCR and serological methods.
¾ Uptake of PCV7 (3 doses) by 24 months of age was 89% for the Q4-2008 birth cohort
Penicillin susceptibility was assessed using the E-Test. Penicillin non-susceptible
S. pneumoniae were defined as an MIC ≥0.12 mg/L.
¾ Four PCV7 vaccine failures have occurred; serotype 14 (n=2) and 19F (n=2)
Since1st December 2010, PCV13 is now being used in Ireland
¾ At HPSC typing data were collated on an MS Access database and analysed using MS
Access and MS Excel.
INTRODUCTION
¾ In September 2008, PCV7 was introduced to the immunisation schedule at 2, 6 and 12 months.
¾ At the same time, a catch-up campaign for children <2 years was also implemented and this was
completed by March 2009.
2007 the National In
asi e Pne
mococcal Disease (IPD) T
ping Project was
as established
¾ In April 2007,
Invasive
Pneumococcal
Typing
established.
¾This project has been pivotal in ascertaining the baseline serotype distribution of IPD isolates prior
to introducing PCV7 and in determining the impact of the immunisation programme on IPD burden
and serotype distribution.
¾The impact of PCV7 on IPD burden in Ireland was determined by comparing data from
April 2007 – September 2008 (pre-PCV7 period) and data from April 2009 – September
2010 (post-PCV7 period) . Isolates from the intermediate period (October 2008 – March
2009) were excluded from the analysis, as this was the period during which the catch-up
programme was being roll out. Specimen date was used to assign each isolate to the
relevant time period.
¾ Enhanced surveillance was completed by the Departments of Public Health on IPD
j
with the typing
yp g
notifications for children born since 2000 and these data in conjunction
data were used by HPSC in monitoring for potential PCV7 vaccine failures.
¾ National immunisation statistics on the uptake of the childhood vaccine s including
PCV7 are collated quarterly by HPSC, based on data provided by Departments of
Public Health.
¾ Other IPD surveillance initiatives in Ireland include monitoring of notification data (clinical and
laboratory) and the enhanced surveillance of IPD cases, with a particular focus on children.
Impact PCV7 on IPD burden
RESULTS
Between April 2007 and September 2010, 1099 invasive S.
pneumoniae isolates were typed (pre –PCV7 period = 491
post = 391 isolates).
)
isolates, inter = 220 isolates and p
Serotype distribution
1a
In total 44 different serotypes were identified.
Serotype 7F has replaced 14 as the most common IPD serotype in
children <2 years of age. There has been a marked decline in
yp 14 related infections. No cases of IPD due to serotypes
yp
serotype
18C and 23F have occurred since PCV7 was introduced (Figure 2).
Overall, the most common serotypes associated with infection prePCV7 introduction were 14, 4, 9V and 7F; post-PCV7 the
predominant serotype is 7F, followed by 14, 19A & 8.
An 83% reduction in IPD infections due to serotypes covered by
PCV7 has been seen in children <2 years of age (Figure 1a and
Table 1).
Although there has been an 24% increase in IPD infections due
to non-PCV7 serotypes in children <2 years of age (Figure 1b
and Table 1), total IPD infections have decline by 55% in this age
group (Table 1).
1b
The burden of IPD infections has declined by 21% when all ages
groups and pneumococcal serotypes are included (Figure 1c).
Table 1. Percentage change in the burden of IPD in Ireland
when the pre- and post-PCV7 periods are compared
Figure 2. Predominant serotypes in children <2 years of age during
the pre- and post-PCV7 periods.
* Denotes serotype covered by PCV7; ^ covered by PCV13
1c
Penicillin non-susceptible S. pneumoniae (PNSP)
The proportion of PNSP isolates remains largely unchanged when
the pre and post periods are compared; 16% and 17%, respectively.
Serotype 9V was the predominant PNSP type pre PCV7, with 80%
of 9V isolates non-susceptible to penicillin. Post PCV7, serotype 14
is the predominant PNSP type, closely followed 9V and 19A.
PCV7 Immunisation Uptake
Uptake of the PCV7 three dose schedule, in children by 24
months of age, was 88% in Q3-2010 (Q3-2008 birth cohort) and
89% in Q4-2010 (Q4-2008) birth cohort.
Figure 1. Cumulative number of IPD cases pre and
post PCV7 introduction, in children <2 years of age
with PCV7 serotypes (1a) and non-PCV7 serotypes
(1b); and in all age groups due to all serotypes (1c)
DISCUSSION
Similar to other countries that have introduced PCV7 to the infant immunisation schedule, Ireland has seen a
marked decline in the burden of IPD particularly in children <2 years of age. In just two years since PCV7 was
i t d
introduced,
d iinfections
f ti
d
due tto IPD PCV7 serotypes
t
have
h
declined
d li d by
b 83% iin thi
this age group.
Post-PCV7, serotype 7F has emerged as the predominant serotype and 19A as the third most common both in
children and in the general population, both of these serotypes are covered by PCV13.
Continued surveillance of IPD including invaluable data from the National Typing Project is essential to monitor
the impact of the PCVs on the burden of IPD in Ireland. Also as newer vaccines are developed and licensed,
the importance of having ongoing and comprehensive typing data is key to informing decisions as to the value
of introducing such vaccines to the immunisation programme in Ireland.
Faculty of Public Health, Summer Scientific Meeting
PCV7 Vaccine Failures
Four PCV7 vaccine failures have been reported in children between
one and three years of age. Two each were associated with
serotype 14 and 19F related infections.
CONCLUSIONS
¾ The introduction of PCV7 to the Irish infant immunisation schedule has dramatically
reduced the burden of IPD, particularly in children <2 years of age.
¾ Further reductions in the burden of illness due to IPD infections is anticipated as PCV13 is
now in use in Ireland since 1st December 2010.
¾ Uptake of the three doses of IPD vaccine needs to be improved, ideally to 95% to ensure
ongoing protection of the most vulnerable in our population.
ACKNOWLEDGEMENTS
The authors would like to thank all those involved in the surveillance of invasive pneumococcal
disease in Ireland. Special thanks to the microbiology laboratories for submitting isolates for typing.
25- 26th May 2011