Comparison of plaque reduction neutralisation test (PRNT) and measles virus-specific IgG ELISA for assessing immunogenicity of measles vaccination

MMR vaccination and disease elimination: the Finnish experience

Measles, mumps and rubella (MMR) vaccinations have been included in Finland's national vaccination program as a two-dose schedule since 1982. Owing to the high (>95%) coverage of vaccinations, indigenous MMR diseases were eliminated from Finland by the mid-1990s. In 1982, the incidence of measles, mumps and rubella was 105, 43 and 64 per 100,000 population, respectively, but declined to 0.1 per 100,000 population for all MMR diseases in 1995. Since then, the few cases of measles, mumps and rubella imported annually have not caused any outbreaks. Several research projects that started along with the vaccination campaign have provided important support throughout the program. The vaccine was proven to be safe, immunogenic and effective. Antibody follow-up has revealed that MMR vaccine-induced antibodies wane over time, and concerns have arisen about the continuation of this good situation. High vaccination coverage, enhanced surveillance and preparedness to administer additional doses when needed are key factors for future success. Here we present an overview of MMR vaccinations and the Finnish experience of the MMR disease elimination process, and we describe surveillance activities in the era following elimination in Finland.

HIV-1 infection in Zambian children impairs the development and avidity maturation of measles virus-specific immunoglobulin G after vaccination and infection

BACKGROUND

Endemic transmission of measles continues in many countries that have a high human immunodeficiency virus (HIV) burden. The effects that HIV infection has on immune responses to measles and to measles vaccine can impact measles elimination efforts. Assays to measure antibody include the enzyme immunoassay (EIA), which measures immunoglobulin G (IgG) to all measles virus (MV) proteins, and the plaque reduction neutralization (PRN) assay, which measures antibody to the hemagglutinin and correlates with protection. Antibody avidity may affect neutralizing capacity.

METHODS

HIV-infected and HIV-uninfected Zambian children were studied after measles vaccination (n=44) or MV infection (n=57). Laboratory or wild-type MV strains were used to infect Vero or Vero/signaling lymphocyte-activation molecule (SLAM) cells in PRN assays. IgG to MV was measured by EIA, and avidity was determined by ammonium thiocyanate dissociation.

RESULTS

HIV infection impaired EIA IgG responses after vaccination and measles but not PRN responses measured using laboratory-adapted MV. Avidity was lower among HIV-infected children 3 months after vaccination and 1 and 3 months after measles. Neutralization of wild-type MV infection of Vero/SLAM cells correlated with IgG avidity.

CONCLUSION

Lower antibody quality and quantity in HIV-infected children after measles vaccination raise challenges for assuring the long-term protection of these children. Antibody quality in children receiving antiretroviral therapy requires assessment.