Pertussis outbreak in an elementary school with high
vaccination coverage.
Khetsuriani N, Bisgard K, Prevots DR, Brennan M, Wharton M, Pandya S, Poppe
A, Flora K, Dameron G, Quinlisk P.
National Immunization Program, Centers for Disease Control and Prevention,
Atlanta, GA 30333, USA. nkhetsuriani@cdc.gov
BACKGROUND: An outbreak of pertussis in a US elementary school with high
vaccination coverage was investigated to evaluate vaccine effectiveness and to
identify potential contributing factors. METHODS: Survey and cohort study of
all 215 students of an elementary school (including 36 case patients) and 16
secondary cases among contacts. RESULTS: Fifty-two pertussis cases were
identified (attack rate among students, 17%). Receipt of <3 doses of
pertussis-containing-vaccine compared with receipt of complete vaccination
series was a significant risk factor for pertussis [relative risk, 5.1; 95%
confidence interval (CI), 3 to 8.6].
The effectiveness of the complete vaccination series was 80% (95% CI 66
to 88). No evidence of waning immunity among students was found. The following
contributing factors for the outbreak were identified: multiple introductions
of pertussis from the community; delays in identification and treatment of
early cases; and high contact rates among students. Antimicrobial treatment
initiated >14 days after cough onset was associated with increased risk of
further transmission of pertussis (relative risk, 10.1; 95% CI 1.5 to 70.3)
compared with treatment within 14 days of onset. CONCLUSIONS:
This investigation demonstrated the
potential for pertussis outbreaks to occur in well-vaccinated elementary
school populations. Aggressive efforts to identify cases and contacts
and timely antimicrobial treatment can limit spread of pertussis in similar
settings. High vaccination coverage should be maintained, because vaccination
significantly reduces the risk of the disease throughout the elementary school
years, and to ensure timely diagnosis and treatment health care providers
should maintain a high index of suspicion for pertussis among elementary
school age children.
Efficacy of acellular pertussis vaccine in young infants.
Aoyama T, Iwata T, Iwai H, Murase Y, Saito T, Akamatsu T.
Department of Pediatrics, Kawasaki Municipal Hospital, Japan.
A prospective study of a pertussis outbreak in a residential facility was done.
Among 19 residents aged < or = 2 years, 10 children were unimmunized and 9 were
immunized with acellular pertussis vaccines. Of the 10 unimmunized children, 7
acquired laboratory-confirmed pertussis (four-fold titer rise, positive culture,
or both); of these, 6 developed typical symptoms. Eight of the 9 immunized
children acquired laboratory-confirmed infections, and 1 of these developed
typical symptoms. No difference in
infection was noted between the
unimmunized and immunized groups
(7/10 vs. 8/9, respectively), but a significant difference was observed in the
development of symptoms (6/10 vs. 1/9, P < .05). Also, the isolation rate
of Bordetella pertussis seemed to differ between the two groups (6/10 vs. 2/9, P
= .12). In this population, acellular pertussis vaccine did not prevent
infection with B. pertussis but protected most young infants from the onset of
clinical symptoms.
PMID: 8421187 [PubMed - indexed for MEDLINE]
Comment: Is pertussis spread by asymptomatic infection?
Vaccine efficacy and control measures in pertussis.
Palmer SR.
PHLS Communicable Disease Surveillance Centre, Welsh Unit, Roath, Cardiff.
An outbreak of pertussis in primary school-children in the St David's area of
Pembrokeshire provided the opportunity to estimate pertussis vaccine efficacy.
The estimate of efficacy was 88% when
notified cases were used, but this fell to 68% when all children with bouts of
coughing for two or more weeks were included. Notified cases were
significantly less likely to have been vaccinated than other cases with similar
symptoms. Therefore vaccine efficacy estimates based upon notified cases are
likely to be biased. However, even the lower estimates suggest that pertussis
immunisation is highly desirable and efforts to improve coverage should be
increased.
Saito T, Akamatsu T, Aoyama T, Iwai H, Gonda T, Murase Y, Yamshita N, Iwata
T.
Azabu Nyujiin, Tokyo, Japan.
An outbreak of pertussis occurred in one room of a residential facility where 19
children aged 5 to 36 months were residing. They were prospectively surveyed to
estimate the efficacy of acellular pertussis vaccine. Among the 19 residents, 9
were immunized with acellular pertussis vaccine. Among the 19 residents, 9 were
immunized with acellular DTP vaccine and 10 were unimmunized. The spread of
pertussis was surveyed bacteriologically and serologically for 2 months.
Among the 9 immunized, 7 children
acquired the laboratory-confirmed pertussis and 1 of the 7 developed the typical
symptoms (whooping or paroxysmal coughing attack lasting for 14 days or more).
Among the 10 unimmunized, 7 children acquired the laboratory-confirmed pertussis
and 6 of the 7 developed the typical symptoms. There was no difference in the
rate of secondary infection (7/9:7/10), but there was a significant difference
in the rate of development of the typical symptoms (1/7:6/7 p less than 0.05).
The point estimate of protective
efficacy of the acellular DTP vaccine against typical pertussis was (6/10 -
1/9)/(6/10) x 100 = 81%. It was concluded from these findings that
acellular DTP vaccine could not prevent the infection of Bordetella pertussis,
but could prevent the development of the typical symptoms.
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