MEASLES VACCINATION IN HEALTH CARE PERSONNEL

Tuesday, 17th of July 2012

• MEASLES VACCINATION IN HEALTH CARE PERSONNEL

Sabine Wicker and Gregory Poland, Vaccine, May 2012

Global measles cases have declined dramatically over the last decade, to a new “low” of an estimated 20 million cases annually, with 164,000 deaths. Unfortunately, however, this obscures an important trend worth noting. In the U.S., much of Europe, and elsewhere, the number of measles cases has been increasing as parts of the population and even healthcare personnel (HCP) fail to be immunized [1], as well as among those who received vaccine, but experienced primary or secondary vaccine failure. In 2011, the U.S. had more recognized measles cases (an estimated 244) than in any of the past 10 years. This is in spite of the fact that in the U.S., measles was declared eliminated in 2000 [2]. Among 33 European countries, more than 30,000 known cases have recently occurred [3]. 

Importantly, the goal of eliminating measles by 2010 has not been achieved and it is very unlikely that this will be achieved by 2015, which is the new WHO target for elimination of measles [4]. Multiple previous measles elimination goals have been set, and none have been met.  

Among the difficulties in measles elimination and eradication is the fact that measles is the most transmissible human disease known, requiring very high population-level immunity. For this reason, even a single case of measles in a healthcare setting can result in a nosocomial outbreak and deserves immediate action [5]. Given their professional duties, and the increasing numbers of cases to which they may be exposed, it is not surprising that HCP are at substantially higher risk than the general population for becoming infected with measles, and transmission occurs within medical facilities due to HCP [6–11]. In one study, HCP were 19 times more likely to be infected than other adults [8]. During the measles resurgence of 1989–1991, medical settings constituted a highly significant site of measles transmission [6,12,13]. Despite this, only three states in the U.S. mandate that hospital personnel be immune to measles [6,14]. Importantly, non-immune HCP pose a risk to themselves and to others (e.g., patients, colleagues, and family); therefore, the moral, ethical, and perhaps legal onus for protection lies not only with occupational vaccination programs in the institutions within which HCP work, but also with HCP themselves.

Current recommendations in the U.S. for HCP are that all “HCP who work in medical facilities should be immune to measles, mumps, and rubella [6].” HCP who were born in 1957 or later are considered immune only if they have laboratory confirmation of immunity or documentation of having received two appropriate doses of vaccine. The recommendations go on to state that while birth prior to 1957 is acceptable evidence of immunity, “healthcare facilities should consider recommending two doses of MMR vaccine routinely to unvaccinated HCP who do not have laboratory evidence of immunity [6].” Two doses of measles vaccine provide long-lasting immunity in nearly all recipients; a two-dose vaccine effectiveness of 99% has been described by the Centers for Disease Control and Prevention [15], but we would contend that these estimates are inflated by results from highly controlled clinical trials, and not routine field use in clinical practice. Nonetheless, for HCPs who have two documented doses of measles vaccine, serologic testing is not recommended by the Advisory Committee on Immunization Practices (ACIP) [6].

Similarly, the German Standing Committee on Vaccination (STIKO) does not recommend serologic testing for HCP. In Germany a two-dose measles vaccination program (first dose at age 11–14 months and a second dose between 15 and 23 months) is recommended.  

In addition, HCP who were born after 1970 and who do not know their vaccination status, or who have never been vaccinated against measles or who have been vaccinated only once during childhood, should receive one additional measles vaccination. Remarkably, in Europe only Finland has established a policy for mandatory measles vaccination for HCP. At the current time half of European countrieshave no recommendations or requirements for HCP measles vaccination [16].However, as discussed, measles vaccines are not 100% protective against subsequent disease, and in part this relates to evidence of both primary and secondary vaccine failure [17]. Published formal clinical trials demonstrating extremely high rates of seroprotection are not directly generalizable to the general population. In clinical trials, clinical subjects are healthy and highly selected, and vaccines are stored and administered according to strict protocols that are not in place during routine field or clinical use. In a variety of studies, for example, measles vaccine has had a failure rate measured at 2–10% and immunity can and does wane over time allowing for future infection upon exposure [9–11,13,18–20]. For this reason,measles outbreaks have been reported in highly vaccinated communities, and this seeming paradox has been previously discussed [21,22]. In a measles outbreak in Canada, more than 50% of the 98 individuals involved had received two previous doses of measles vaccine [22,23] and measles infections have been described even after three doses of vaccine [24].

This is clear evidence of the need for a second generation, more highly immunogenic measles vaccine, ideally only requiring a single dose [23].

Chen et al. recommended that “because performing rapid serology testing during an outbreak is costly and disruptive, healthcare facilities should have serologic evidence of immunity available for all HCP to facilitate rapid vaccination response during a measles outbreak [9].” However, the sensitivity of the various serologic tests might distort the actual rate of humoral immunity, as different laboratories use different assays for measuring humoral immunity (i.e., neutralization assays, EIA assays, and indirect immunoflourescence assays, etc.), and HCP personal history of immunity may not be reliable [25]. Too, it is important to note that serologic assays of humoral immunity appear to be independent of cellular immune responses to measles [26]. 

Measles is a serious global public and occupational health problem. Nosocomial outbreaks are costly and highly disruptive [8,9,20], and are associated with increased HCP absenteeism and medical leave, and more importantly with transmission to highly vulnerable patients. We believe that it is imperative that all HCP have documented and easily retrievable evidence of measles immunity to ensure case management and rapid outbreak response [6,9]. To protect the public and the patients we serve, receipt of appropriate measles immunization(s) should be mandatory, absent a valid medical contraindication, for all HCP. In addition, further thought must be given for requiring measles serology among individual HCP where the risk of non-immunity may be higher (i.e., HCP unable to receive vaccine, immunocompromised HCP, those HCP who received vaccine at an earlier than recommended age in infancy, or HCP who received vaccines of unknown efficacy, type, or handling in other countries). The data clearly demonstrating the higher risk of HCP being exposed to measles, the increasing number of recent cases, the associated morbidity and mortality of the disease, the economic costs of containing an outbreak, the extreme disruption of nosocomial measles, and the risk of transmission to patients and other healthcare staff, as well as the demonstrated safety and efficacy of the vaccine; provide a solid basis for such a mandate. HCP, their patients, fellow staff, and the public deserve to know that as a profession we take prevention of highly transmissible diseases seriously, and hold ourselves accountable to the highest possible standard to protect them. 

Disclosures

Dr. Poland serves on a data management and safety committee for non-measles investigational vaccines being developed by Merck Research Laboratories. He also serves as the American College of Physician’s liaison member to the Advisory Committee on Immunization Practices.

Dr. Wicker is a member of the German Standing Committee on Vaccination (STIKO). 

The views in this article are the personal views of the authors and do not necessarily represent the views of the professional organizations or institutions within which we are members.

© 2012 Elsevier Ltd. All rights reserved.

http://dx.doi.org/10.1016/j.vaccine.2012.05.015

Editorial / Vaccine 30 (2012) 4407– 4408

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Sabine Wicker Occupational Health Service, Hospital of the Johann Wolfgang Goethe-University, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany

Editor-in-Chief

Gregory A. Poland∗

Mayo Vaccine Research Group, Mayo Clinic and Foundation, Rochester, MN 55905, United States

∗ Corresponding author. Tel.: +1 507 284 4968; fax:

+1 507 266 4716.

E-mail addresses: Sabine.Wicker@kgu.de (S.Wicker), Poland.gregory@mayo.edu (G.A. Poland)

10 May 2012