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New employees come in with a record of immunizations, but no detectable antibody response. Or employees receive the hepatitis B series, but don’t show an antibody response. What do you do? Here are some questions and answers about health care worker immunizations, based on guidelines from the Centers for Disease Control and Prevention in Atlanta:
Q. If employees at risk for bloodborne pathogen exposure received their full series of vaccinations, is it necessary to conduct tests for antibody to hepatitis B surface antigen? What should you do if the test is negative?
A. Health care workers should be tested for antibody to hepatitis B surface antigen (anti-HBs) one to two months after completing the three-dose vaccination series. If an employee does not respond, the series should be repeated and the employee retested for anti-HBs. Those who still don’t respond should be evaluated to determine if they are HBsAg-positive. Those who are HBsAg-negative but do not respond to the vaccination should be considered susceptible to HBV and should be counseled on precautions. In the case of exposure, they should receive HBIG prophylaxis. The Occupational Safety and Health Administration made reference to the CDC guidelines in its most recent needlestick prevention compliance directive (November 1999), so OSHA inspectors and/or Joint Commission on Accreditation of Healthcare Organizations surveyors may ask for documentation of post-vaccine titers.
Q. If an employee delays the second dose of the HBV vaccine for six months or more, should you start the series over? What is the optimal timing of the doses?
A. Optimal antibody titers are produced by an interval of at least one month between the first two doses and at least five months between the second and third doses. The longer the time interval between the second and third doses, the better the antibody response. No matter when previous doses were given, it is safe and effective to simply resume the immunization schedule where it was left off.
Q. Which vaccinations require a booster? What if HBV or rubella titers decline?
A. Vaccine-induced antibodies to HBV decline over time. However, booster doses of hepatitis B vaccine are not considered necessary, and periodic serologic testing to monitor antibody concentrations after completion of the vaccine series is not recommended. Those born before 1957 usually are considered immune to rubella and measles. However, findings of seroepidemiologic studies indicate that about 6% of HCWs (including those born in 1957 or earlier) do not have detectable rubella antibody. If health care workers over 60 do not have documentation of rubella immunity, they should be tested for rubella-specific IgG. If they have an IgG value above the range considered immune on the assay, they are considered immune. If not, they should be vaccinated. Rubella titers do decline over time, but studies have shown that the majority of individuals with low titers do mount a response when challenged with rubella virus. The rubella vaccine failure rate is 5%, and one dose of a rubella-containing vaccine is thought to provide lifelong immunity. Thus, booster doses are not considered necessary, and periodic serologic testing to monitor immunity levels is not recommended.
Q. If health care workers receive a varicella vaccine, should they be considered adequately protected?
A. Some 99% of those vaccinated against varicella become seropositive after the second dose. Seroconversion, however, does not always result in full protection against disease. One potentially effective strategy is to test vaccinated people for serologic evidence of immunity immediately after they are exposed to VZV. Prompt, sensitive, and specific serologic results can be obtained at reasonable cost with a commercially available latex agglutination test. However, even an employee who is tested following exposure and determined to have antibodies should be followed closely in case he or she develops breakthrough disease. People with detectable antibodies are unlikely to become infected with varicella. Exposed people who do not have detectable antibodies can be retested in five to six days. If an anamnestic response is present, these people are unlikely to contract the disease. HCWs who do not have antibody when retested may be furloughed. Their clinical status may be monitored daily; they can be furloughed at the onset of varicella manifestations.
Q. What is the incidence of side effects among women to the MMR vaccine?
A. Arthritis is the most significant side effect of rubella vaccination, particularly in adult women. Adverse event reporting following MMR vaccination indicated that 26.4% of seronegative adult females had joint manifestation. A review of adverse events from Canada gave a reaction rate for rubella vaccine of 28.7 per 100,000 doses distributed, of which 0.3 per 100,000 was arthritis or arthralgia. However, much information on joint reactions was obtained studying the HPV-77 strain of vaccine, which is no longer used in the United States. This strain was particularly likely to cause joint reactions, even among children. The RA27/3 strain, currently used in the United States, has a lower reported incidence of joint manifestations (20-25%), but only about 1% of seronegative female vaccinees miss days of work due to joint pains. Other side effects include lymphadenopathy, sore throat, and headache. The incidence and severity of reactions is greatest in older women. The CDC notes that side effects are rarely significant enough to result in lost workdays.
(Editor’s note: Miriam Alter, PhD, chief, epidemiology section, division of viral hepatitis, and Jane Seward, MBBS, MPH, acting chief, child vaccine preventable disease control branch of the National Immunization Program, contributed information for this article.)
Source: Immunization of Health Care Workers: Recommendations of the Advisory Committee on Immunization Practices (ACIP) and the Hospital Infection Control Practices Advisory Committee (HICPAC). MMWR 1997; 46(RR-18):1-42.