Sustained transmission of mumps in a highly vaccinated population: assessment of primary vaccine failure and waning vaccine-induced immunity

Serologic response to measles-mumps-rubella vaccine among children with upper respiratory tract infection

The influence of concurrent upper respiratory tract infection (URTI) on immune response to MMR (measles, mumps, rubella) vaccine was evaluated by measuring IgG levels for each viral component immediately before vaccination and 6 months after vaccination in 198 12-month-old children (101 children without URTI and 97 with URTI at time of vaccination). None of the children had antibodies to measles, mumps or rubella before vaccination. Seroconversion rates and the geometric means of the antibody titers in children without URTI and in children with URTI at the time of vaccination were similar. MMR vaccination should not be delayed in children with such infections.

An outbreak of mumps in a population partially vaccinated with the Rubini strain

Since 1991, 6 years after the recommendation of universal childhood triple vaccination against measles, mumps and rubella (M + M + R), Switzerland has been confronted with an increasing number of mumps cases affecting both vaccinated and unvaccinated children. The M + M + R vaccine mainly used in the Swiss population after 1986 contains the highly attenuated Rubini strain of mumps virus. We analysed an outbreak of 102 suspected mumps cases by virus isolation, determination of IgM antibodies to mumps virus in 27 acute phase sera, and verification of vaccination histories. Mumps was confirmed by virus isolation in 88 patients, of whom 72 had previously received the Rubini vaccine strain. IgM antibodies to mumps virus were detected in 24/27 acute phase serum samples. A group of 92 subjects from the same geographic area without signs of mumps virus infection served as controls. IgG antibodies to mumps virus and vaccination status were assessed in these children. The vaccination rate in these controls was 61%, with equal seropositivity for unvaccinated and Rubini-vaccinated subjects. These data support other recent reports which indicate an insufficient protective efficacy of current mumps vaccines.

[Comparison of the efficacy of various strains of mumps vaccine: a school survey]

BACKGROUND

Since the beginning of the program of immunization of children against measles, mumps and rubella (MMR) in 1987, various outbreaks of mumps have occurred in Switzerland, with a significant proportion of cases in immunized children. Previous studies have suggested a possible lack of efficacy of the Rubini vaccine strain, which has been much used in this country.

METHODS

Incidence study of secondary cases of mumps in the schools of Geneva, between March 18th and June 30th 1994.

STUDY POPULATION

During the study period, mumps outbreaks have been observed in 10 school classes. After exclusion of the 10 primary cases, the study population comprised 195 children aged 4 to 12 years.

RESULTS

Raw estimation of vaccine efficacy against mumps was 72.5%. Whereas both the Urabe and Jeryl-Lynn strains showed a significant efficacy, the Rubini strain didn't show any significant protective effect. After adjustment by Poisson regressions for the confounding effect of age, efficacy rates and 95% confidence limits were 75.8% (35.6%, 90.9%) for Urabe; 64.7% (10.6%, 86.0%) for Jeryl-Lynn; and 12.4% (-102%, 62.1%) für Rubini.

CONCLUSION

This study didn't show any protective effect of the Rubini vaccine strain. Furthermore, it demonstrated a statistically significant protective effect of the Urabe and Jeryl-Lynn strains, compared to the Rubini strains. In this conditions the use of the Rubini strain should be restricted to situations of confirmed contra-indications to the other vaccinal strains, as long as its protective efficacy is not clearly demonstrated.

Persistence of anti-mumps virus antibodies after a two-dose MMR vaccination. A nine-year follow-up

A two-dose vaccination program against measles, mumps, and rubella (MMR) viruses was started in Finland in 1982. In this program the trivalent MMR-II vaccine (MSD, USA) was offered to children at the ages of 14-18 months and 6 years followed by revaccination 4-5 years later. The vaccination coverage has been high (97%) and MMR infections have practically been eliminated in the Finnish population. In a serological follow-up program sequential serum samples were obtained from 254 children (127 14-18-month-old vaccinees and 127 6-year-old vaccinees) during a 9-year follow-up period. Anti-mumps virus antibody titers were determined by enzyme immunoassay using purified whole mumps viruses as the antigen. In seronegative (n = 120) 14-18-month-old vaccinees the seroconversion rate was 86% (geometric mean titer 1/1670 +/- 1/270). The antibody levels fell rapidly (significance p < 0.01) within the first year of follow-up (mean titer 1/1080 +/- 1/190), but remained relatively stable in subsequent years. After revaccination the seropositivity rate was 95% (mean titer 1/2310 +/- 1/260) and declined more slowly thereafter to 86% (mean titer 1/1510 +/- 1/210) at year 9 of follow-up. The mean antibody titer was significantly (p < 0.05) higher 4 years after the second MMR vaccination when compared with the corresponding time point after the first vaccination. In 6-year-old seronegative vaccinees the increase and decay of anti-mumps virus antibodies after the first MMR vaccination was similar to that seen in the group of younger vaccinees. A two-dose MMR vaccination protocol resulted in a high mumps immunity level in the vaccinated population.

Measles, mumps, and rubella antibodies in children 5-6 years after immunization: effect of vaccine type and age at vaccination

The levels of antibody against measles, mumps, and rubella were determined at 5-6 years postimmunization in 468 children vaccinated with two different trivalent vaccines. The proportions of children without detectable antibody levels were 12 and 3.6% for measles (p < 0.001), 14.9 and 7% for mumps (p = 0.006), and 3.3 and 3.1% for rubella (p = 0.88), respectively, in MMR II and Trivirix recipients. A higher proportion of those vaccinated at younger ages had undetectable or low levels of measles antibody. These data indicate that a large proportion of children vaccinated under routine conditions do not have detectable measles and mumps antibody.

[Mumps epidemiology in Switzerland: results from the Sentinella surveillance system 1986-1993. Sentinella Work Group]

Since 1990, there have been reports of an increasing number of mumps cases in Switzerland, in particular among vaccinated children, and of local outbreaks of mumps. Using data from the Sentinella reporting system, a network of voluntary participating doctors (general practitioners, internists and paediatricians, yearly average: n = 141), trends and factors influencing mumps incidence in the general population were assessed during the last seven years. Following an initial decline in mumps reports, since 1990, there has been a continuous and marked increase in reports from a minimum of 0.7 cases per physician and year in 1989/90 to a near five-fold increase of 3.3 cases in the last reporting period from June-December 1993 (calculated for one year). Half of this increase, which is reflected in a doubling of the number of cases reported in 1986/87, is explained by an increase in cases among vaccinated children. The trend in mumps cases contrasts with that of measles and rubella, where there has been a clear decline in these reports since 1986 (approximately 70-80%). Complications were reported in 75 (4.0%) of the total number of mumps patients (n = 1894); in 2/5 of the cases this was a meningitis, in 1/3 an orchitis. Based on available data on vaccination coverage, the estimated efficacy of the mumps vaccines against parotitis is between 47-77%; this is clearly lower than the corresponding figure for measles (91-97%) and rubella (89-97%) vaccines. The relatively low efficacy against parotitis is mainly due to a protective level of 13-73% of the vaccines containing the Rubini strain. The estimated efficacy of the Rubini vaccines against complications is 50-81%; it is nearly 60-90% if a possible reporting bias is taken into consideration.

CONCLUSIONS

1. The Rubini strain vaccines, which are the most commonly used in Switzerland, seem to have played an important role in the clear increase in mumps cases since 1990. 2. The situation seems more favourable concerning the efficacy against complications of the vaccines used. 3. Our data support the high efficacy of all measles and rubella vaccines. 4. The surveillance of MMR by the Sentinella reporting system provides a useful and effective manner to evaluate the MMR vaccination programme.

[Mumps epidemiology--worldwide]

Mumps is an acute viral infection that is endemic worldwide and that occurs primarily in school-age children and adolescents. The most prominent manifestation is tender swelling of the parotid gland. The course of the disease is usually mild and selflimited. Meningitis and orchitis, the latter more common in postpubertal persons, are less frequent manifestations of this disease. As characteristic of many viral infections the severity of the illness increases with age. In the present review first the most important epidemiologic parameters of mumps are presented, as well as the various clinical manifestations and complications. Further the epidemiology of mumps in developing and in industrialized countries is discussed. Breakthrough infections with mumps occurring with either low or high vaccination coverage are described.

[Mumps vaccines: vaccination failures from an immunological viewpoint]

The significance of mucosal and systemic immunity is illustrated with the example of the different immune response of Poliovaccine live oral (Sabin) and Poliovaccine inactivated parenteral (Salk). On the occasion of rubella- and measles-outbreaks it will be demonstrated that in vaccinated people subclinical reinfections may much more frequently occur than clinically manifest diseases. On the basis of these findings one may consider the large number of parotitis cases without complications in mumps vaccinated Swiss pupils as secondary mucosal vaccine failures at a time, when systemic immunity still was protective. Significance for vaccination policy and consequences for handling of vaccines shall be briefly discussed.