BACKGROUND: Studies in Japan and the United States have shown that varicella vaccine is both safe and efficacious. In 1984, we undertook a 10-year prospective study using a research lot of Oka/Merck varicella vaccine to assess antibody persistence and breakthrough @entity992 rates. In 1987, we began a similar prospective study with lots made in production facilities that ended after 6 years because many @entity1 were given a second dose. The purpose of this study is to report humoral antibody persistence and breakthrough @entity992 rates after 6 to 10 years of prospective follow-up. METHODS: One hundred forty-three seronegative @entity1 received a research lot (950 plaque-forming units/dose) with 97.9% seroconversion by an assay for fluorescent antibody to membrane antigen (FAMA). One hundred thirty-eight @entity1 received production lots (1145 to 3265 plaque-forming units/dose) with 93.5% seroconversion. Yearly @entity992 exposure surveys were completed by phone, and @entity1 were seen by a study nurse whenever @entity992 was suspected. A subset in each group had serum collected every 2 years and tested for FAMA antibody. RESULTS: In the research group there have been 25 cases of @entity992 in 137 seroconverters in a period of more than 10 years (yearly rate of 1.7%). In the production lot group there have been 22 cases of @entity992 in 129 seroconverters in a 6-year period (yearly rate of 2.8%). In the research group the median titer rose from 1:16 to 1:64 between 1 and 10 years. In the production group, the median titer did not change between 1, 2, and 4 years. Median antibody titers were compared between the research and production groups at 1, 2, and 4 years and did not differ. The rate of development of modified @entity992 has not increased with time since vaccination, and neither has the case severity. @entity1 with FAMA titers </=8 at 6-weeks' postvaccination were four times more likely to develop @entity992 than those with titers >/=64. CONCLUSIONS: 1) Modified @entity992 has occurred in approximately 2% to 3% of vaccinees per year, regardless of the vaccine lot given. 2) FAMA titers have risen between 1 and 10 years in research lot recipients and remained the same in production lot recipients. 3) The likelihood of modified @entity992 developing is inversely related to the 6-week postvaccination FAMA titer.

A long-term prospective study of varicella vaccine in healthy XXXX .

@entity1 :: ('9606', 'Species') :: ['children', 'Children'] @entity992 :: ('MESH:D002644', 'Disease') :: ['chickenpox']
@entity1 :: (9606,Species) :: ['children']
