Paunio M, Hedman K, Davidkin I, Valle M, Heinonen OP, Leinikki P, Salmi A, Peltola H. Department of Public health, University of Helsinki, Finland. Secondary measles vaccine failures identified by measurement of IgG avidity: high occurrence among teenagers vaccinated at a young age. Epidemiol Infect 2000 Apr;124(2):263-71

Failure to seroconvert (primary vaccine failure) is believed to be the principal reason (approx. > 95%) why some vaccinees remain susceptible to measles and is often attributed to the persistence of maternal antibodies in children vaccinated at a young age. Avidity testing is able to separate primary from secondary vaccine failures (waning and/or incomplete immunity), but has not been utilized in measles epidemiology. Low-avidity (LA) and high-avidity (HA) virus-specific IgG antibodies indicate primary and secondary failure, respectively. Measles vaccine failures (n = 142; mean age 10.1 years, range 2-22 years) from an outbreak in 1988-9 in Finland were tested for measles-virus IgG avidity using a protein denaturating EIA. Severity of measles was recorded in 89 failures and 169 non-vaccinees (mean age 16.2 years, range 2-22 years). The patients with HA antibodies (n = 28) tended to have clinically mild measles and rapid IgG response. Among failures vaccinated at < 12, 12-15 and > 15 months of age with single doses of Schwarz-strain vaccine in the 1970s, 50 (95% CI 1-99), 36 (CI 16-56) and 25% (CI 8-42) had HA antibodies, respectively. When a single measles, mumps and rubella (MMR) vaccine had been given after 1982 at 15 months of age, only 7% (CI 0-14) showed HA antibodies. Omitting re-vaccinees and those vaccinated at < 15 months, Schwarz-strain recipients had 3.6 (CI 1.1-11.5) higher occurrence of HA responses compared to MMR recipients. Apart from one municipality, where even re-vaccinees had high risk of primary infection, 89% (CI 69 to approximately 100) of the infected re-vaccinees had an HA response. Secondary measles-vaccine failures are more common than was more previously thought, particularly among individuals vaccinated in early life, long ago, and among re-vaccinees. Waning immunity even among individuals vaccinated after 15 months of age, without the boosting effect of natural infections should be considered a relevant possibility in future planning of vaccination against measles.

Source: PubMed ID: 10813152