http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9447754&dopt=Abstract
High incidence of breakthrough varicella observed in healthy
Japanese children immunized with live attenuated varicella vaccine (Oka strain).
Takayama N, Minamitani M, Takayama M.
Department of Pediatrics, Tokyo Metropolitan Komagome Hospital, Japan.
In order to know the rate of occurrence of varicella among vaccinees
(breakthrough varicella: BV), questionnaire postcards were sent to 593 healthy
children who had received varicella vaccine (Oka strain) from March 1987 to
December 1989. The questionnaire survey was repeated once a year until January
1996. The annual attack rate from the 1st to 3rd questionnaire was approximately
12%: however, from the 5th to 8th one it was 1-4%. To February 1996, the
cumulative attack rate was 157/459 (34.2%). This rate was comparable to that
among vaccinees who had confirmed seroconversion; namely, 51/132 (38.6%). These
rates are much higher than those reported by other authors. All BV cases were
clinically mild; even subjects who had received the vaccine 7 years prior to the
disease showed mild symptoms. The high incidence may be partly explained by the
regional epidemiology of varicella. The decrease in annual incidence with time
after vaccination may be due to the following reasons: some vaccinees remained
free from BV owing to reinforcement of their immunity from subclinical infection
of varicella-zoster virus (VZV) and others from diminution of opportunity for
exposure to VZV with increasing age. Varicella vaccine seems to be effective in
modifying the symptoms of varicella, but not potent enough in protecting from
VZV infection.
PMID: 9447754 [PubMed - indexed for MEDLINE]
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