Measles Virus-Specific Antibody Levels in Individuals in Argentina Who Received a One-Dose Vaccine

Abstract

In spite of active measles virus (MV) vaccination strategies, reemergence continues to occur, impairing global eradication programs. The immune status against measles was evaluated in 350 vaccinated healthy Argentine children and teenagers who received a single dose of the MV Schwarz strain Lirugen vaccine (Aventis Pasteur). Sera were assessed for immunoglobulin G (IgG) antibodies by a commercial enzyme immunoassay (EIA) (Enzygnost; Behring), an in-house EIA, and neutralization EIA. Results obtained with these methods showed a marked decline in IgG level with increasing age. At 1 to 4 years of age, 84% of children had IgG antibodies above 200 mIU/ml, conventionally accepted as protective levels, whereas only 32% of older children and teenagers had antibody levels exceeding 200 mIU/ml. Moreover, the MV IgG content in the teenage group was significantly lower than the IgG antibody level of the group of younger children (P < 0.0001). In contrast, screening for IgG antibody levels to inactivated tetanus vaccine showed that, on average, 80% of this population was fully protected and that this high level of protection remained through the teenage years. This study suggests that within this population a considerable proportion of individuals had low measles antibody levels that may be insufficient to protect against reinfections or clinical disease.In the early 1960s, the advent of a live attenuated measles virus (MV) vaccine dramatically reduced the incidence of measles in many parts of the world, including developed (12,16,20,29,30,35,49,52) and developing (28, 58) countries. In some developing countries, fatality rates for measles can still be as high as 15%, causing about 770,000 annual deaths among infants and children, and this is probably due to lack of vaccination of many individuals in the population.Elimination of MV requires the continued commitment to increase vaccination coverage levels, the genetic analysis of circulating strains, and serosurveys of vaccinated individuals to establish the population at risk of contracting the infection. In this context, it is very important that reliable and sensitive laboratory methods are used to accurately determine the antibody level and protection achieved after vaccination and the level of antibodies that persists in those who were previously vaccinated.Despite active vaccination strategies, reemergence or resurgence of MV continues to occur, impairing elimination programs. The occurrence of several measles outbreaks in highly immunized populations (5, 34, 40, 51) has focused attention on vaccine efficacy and the durability of vaccine-induced immunity. It is likely that many factors contribute to the presence of susceptible individuals among highly vaccinated populations. These include failure to seroconvert and decline of immunity with time after vaccination (19, 37). Other important factors that might influence the immune response comprise the age at the time of vaccination (27, 33), the number of doses, and the strain included in the vaccine (18,23,28).High vacci...

Low titers of measles antibody in mothers whose infants suffered from measles before eligible age for measles vaccination

“…Thus, it is difficult to compare our measles IgG levels with other reports and with the conventionally accepted protective level of 200 mIU/ml [12]. However, as reported by others [13], we found that our ELISA measles IgG levels were generally correlated with the neutralizing titers (Table 1).…”

Vaccinated students with negative enzyme immunoassay results show positive measles virus-specific antibody levels by immunofluorescence and plaque neutralisation tests

“…Interestingly in countries with high vaccination coverage and low measles incidence remarkably high rates of equivocal sera (15-25%) were noted in this age group. An increase of the portion of seronegative individuals as well as a decline of the mean antibody levels several years after measles vaccination was reported especially from countries where the measles incidence was very low, thus limiting the possibility for natural boosters (Argüelles et al, 2006;Davidkin and Valle, 1998;Miller et al, 1995;Pebody et al, 2002;Ratnam et al, 1996). After re-vaccination some seronegative individuals developed only temporarily positive antibody levels while others remained negative (Cohn et al, 1994;Matson et al, 1993;Ratnam et al, 1996).…”

A 16-year review of seroprevalence studies on measles and rubella

“…Adolescent and young adults aged between 15 and 30 years were identified as a group that may require booster vaccination. Several studies showed that, by this age, the level of measles and rubella antibodies were lower than other age groups studied [11,18,22,24,26,29,30,32,36,42,84,88,91,96]. Several authors recommended that teens be re-vaccinated [24,32,36,42].…”