Imported measles and implications for its elimination in Taiwan

Measles immunity in medical center staff after changes in national and local hospital vaccination policies

Background

Measles vaccination was introduced in Taiwan in 1978, and the disease was declared eliminated in Taiwan in 2007. However, new cases have been reported unpredictably since then. Hospital medical staff are at particularly high risk for measles. We evaluated the immunity status of hospital medical staff after changes in national and local hospital vaccination policies.

Methods

This retrospective study was conducted in a tertiary care medical center from January 2008 to June 2018. Data were retrieved from all healthcare workers receiving employment medical examinations. Those with a full medical record including the geometrical mean titer (GMT) of anti-measles IgG were included. Age and sex differences in the GMT were analyzed by Student’s t-tests and Chi-squared tests. Univariate and multivariate logistic regression analysis were used to determine the odds of immunity.

Results

The IgG positive rate increased with age group (p < 0.001). Seropositive rates for the birth before 1977 and after 1978 groups were 94.8% and 70.2% (p < 0.001). The odds ratio was also significantly different between both cohorts (1.000 vs. 0.423, p = 0.002). Staff in the examination department showed the lowest positive percentage of 70.3% (95% CI: 66.9–73.7%), whereas staff in preventive and long-term care services disclosed the highest positive percentage of 83.2% (95% CI: 76.1–90.2%). Subgroups 2015, 2017, and 2018 (p = 0.046, 0.046, 0.049), after the vaccination booster policy was launched, showed significant increases in seropositivity.

Conclusions

Immunity efficacy is better in birth groups before 1977, which was highly related to natural infection before national policy launched. The policy of vaccination is an effective method, but medical staff attains inadequate protective antibody levels for maintenance of herd immunity. A pre-employment policy of screening a third booster vaccine of measles (or MMR) is recommended to lower the incidence of disease spreading and avoid outbreaks.

Measles Virus Imported by International Traveler in Jiangsu Province of China, in 2018 and 2019

Measles remains a public health concern in many regions, and the imported measles cases continue to challenge the measles elimination program for most of the countries where measles was verified to be eliminated or approaching elimination. The imported measles cases have been reported since October, 2017, in Jiangsu province, China. In this study, we reported the first imported B3 genotype measles virus from Egypt and the second imported D8 genotype measles virus from Philippines through international traveling. No secondary measles cases were found after these imported cases. Our findings highlighted the importance of measles vaccination targeting international travelers in China.

Hospital preparedness in community measles outbreaks-challenges and recommendations for low-resource settings

We have reviewed various strategies involved in containment of measles in healthcare facilities during community outbreaks. The strategies that are more applicable to resource-poor settings, such as natural ventilation, mechanical ventilation with heating and air-conditioning systems allowing unidirectional air-flow, and protection of un-infected patients and healthcare workers (HCWs), have been examined. Ventilation methods need innovative customization for resource-poor settings followed by validation and post-implementation analysis for impact. Mandatory vaccination of all HCWs with two doses of measles-containing vaccine, appropriate post-exposure prophylaxis of immunocompromised inpatients, and stringent admission criteria for measles cases can contribute toward reduction of nosocomial and secondary transmission within facilities.

Reemergence of measles in South Korea: implications for immunization and surveillance programs

Following the implementation of the national measles elimination program, the Republic of Korea declared in 2006 that measles had been eliminated. However in 2011, a measles outbreak was reported in Gyeongnam Province in the southeastern part of the country. We conducted active case-based surveillance and analyzed the data of cases reported in 2011 to identify the factors contributing to the reemergence of measles in this province. Of 41 confirmed measles cases reported in Korea, 32 were from within the Gyeongnam Province. Among cases identified in the outbreak, 97% had inadequate history of immunization, 28% were not immunized at the recommended ages, and 22% were infants aged 6-11 months. The outbreak involved transmission in 3 hospitals, 1 kindergarten, 1 day-care center, and 3 households. Molecular analysis of measles virus isolates from 11 cases revealed the same D9 genotype, which was the first to be discovered in Korea. In conclusion, inadequate immunization coverage, non-timely immunization, infants under 12 months of age, nosocomial transmission, and international importation may play important roles in the reemergence of measles in Korea during the attempted sustained elimination of the disease.

A global perspective of vaccination of healthcare personnel against measles: systematic review

Measles transmission has been well documented in healthcare facilities. Healthcare personnel who are unvaccinated and who lack other evidence of measles immunity put themselves and their patients at risk for measles. We conducted a systematic literature review of measles vaccination policies and their implementation in healthcare personnel, measles seroprevalence among healthcare personnel, measles transmission and disease burden in healthcare settings, and impact/costs incurred by healthcare facilities for healthcare-associated measles transmission. Five database searches yielded 135 relevant articles; 47 additional articles were found through cross-referencing. The risk of acquiring measles is estimated to be 2 to 19 times higher for susceptible healthcare personnel than for the general population. Fifty-three articles published worldwide during 1989-2013 reported measles transmission from patients to healthcare personnel; many of the healthcare personnel were unvaccinated or had unknown vaccination status. Eighteen articles published worldwide during 1982-2013 described examples of transmission from healthcare personnel to patients or to other healthcare personnel. Half of European countries have no measles vaccine policies for healthcare personnel. There is no global policy recommendation for the vaccination of healthcare personnel against measles. Even in countries such as the United States or Finland that have national policies, the recommendations are not uniformly implemented in healthcare facilities. Measles serosusceptibility in healthcare personnel varied widely across studies (median 6.5%, range 0-46%) but was consistently higher among younger healthcare personnel. Deficiencies in documentation of two doses of measles vaccination or other evidence of immunity among healthcare personnel presents challenges in responding to measles exposures in healthcare settings. Evaluating and containing exposures and outbreaks in healthcare settings can be disruptive and costly. Establishing policies for measles vaccination for healthcare personnel is an important strategy towards achieving measles elimination and should be a high priority for global policy setting groups, governments, and hospitals.

Immunogenicity and safety of combined measles-mumps-rubella-varicella vaccine using new measles and rubella working seeds in healthy children in Taiwan and Singapore: a phase II, randomized, double-blind trial

AIM

This study evaluated the immunogenicity and safety of tetravalent measles-mumps-rubella-varicella (MMRV) vaccine produced with measles and rubella monovalent bulks derived from a newly established working seed virus stock (MMRV(new WS)) compared with the combined MMRV vaccine derived from the current seed virus stock, in Taiwanese and Singaporean children (NCT00892775).

METHODS

Healthy children aged 11-22 mo were randomized to receive two doses of either the MMRV(new WS) vaccine or the MMRV vaccine. Antibody titers against measles, mumps and rubella were measured using ELISA and against varicella using an immunofluorescence assay. The primary objective was to demonstrate non-inferiority of MMRV(new WS) to MMRV in terms of post-dose-1 seroconversion rates, defined as a group difference with a lower limit of the 95% confidence interval greater than -10% for each antigen. Parents/guardians recorded symptoms in diary cards for 43 d after each vaccine dose.

RESULTS

Non-inferiority of MMRV(new WS) to MMRV was achieved for all vaccine antigens. The lower limits of the 95% confidence intervals for group differences (MMRV(new WS) group vs. MMRV) for measles (99.4% vs 100%), mumps (89.7% vs 90.4%), rubella (99.7% vs 100%) and varicella (97.6% vs 92.9%) seroconversion rates were greater than -10%. Mild symptoms including a peak in fever between days 5 and 12, post-dose-1, was observed in both groups.

CONCLUSION

The immune responses elicited by the MMRV(new WS) vaccine were non-inferior to that elicited by the MMRV vaccine for all antigens. Both vaccines exhibited an acceptable safety profile in Taiwanese and Singaporean children.