Vaccination programs for healthcare personnel are of great importance because they are at increased risk for contracting and transmitting infectious diseases.1 Despite this fact, elective medical students working temporarily in hospitals are often not provided with an adequate evaluation of their immunization status. Students can be involved in outbreaks of vaccine-preventable diseases in hospitals thereby contributing to increased morbidity, mortality and adverse economic consequences.2 There is evidence that in many countries most students working in healthcare facilities are not adequately vaccinated.3,4
Similar to specific immunization programs in place for students attending medical schools in North America,5 we initiated an immunization surveillance program at our institution in 1999. Ever since, we have been systematically evaluating the immunization status of medical students with a standardized questionnaire and, if indicated, we offer catch-up vaccinations and anti-hepatitis B (anti-HBs) surface antigen serum antibody testing free of charge. Findings of the program during 2011–2013 are reported here.6
The University Children’s Hospital Basel is a tertiary hospital providing healthcare for children in North-Western Switzerland and has an educational program following the curriculum for medical students at the University of Basel. Students from foreign universities also have access to elective periods at our institution.
All medical students with a rotation in our hospital, usually of 2 or 3 months duration, are eligible for voluntary participation in the systematic immunization surveillance program. On initiation of the elective period, participants complete a standardized questionnaire that is subsequently reviewed by the pediatric infectious disease fellow and the program supervisor (U.H.). Any data queries are discussed with the students on an individual basis and recommended measures are offered free of charge. The following characteristics are obtained and subsequently entered into an electronic database: age, gender, nationality, personal history of vaccine-preventable diseases (of which those for varicella and pertussis are reported here) and a detailed history of all recorded immunizations.
Personal history of vaccine-preventable diseases is categorized by the students as “yes, certain”; “yes, probably”; “yes, possibly” and “no” or “unknown”.
Interpretation of Immunization Status and Consequent Procedures
Immunization status against diphtheria, tetanus and poliomyelitis is considered up to date if a primary immunization series (≥3 doses) had been documented with the last dose <10 years ago. Immunization against pertussis is considered up to date if there was a documented dose <10 years ago, regardless of the total number of vaccine doses. Childhood immunization against pertussis was evaluated separately, that is a minimum of 3 doses was considered appropriate until the age of 6 years. For measles, mumps and rubella (MMR), immunity is considered if ≥2 doses had been documented for each of the 3 live-attenuated vaccine components. Alternatively, in unimmunized individuals, a positive specific IgG-antibody value was accepted as an indication of protection against measles and rubella, respectively. Mumps immunization with Triviraten Berna (Crucell Switzerland AG, CH-6300 Zug, Switzerland) is not considered as an adequate protection against mumps because insufficient effectiveness had been shown for this specific MMR vaccine.7 According to Swiss national immunization guidelines, immunity against HB is defined as ≥3 recorded vaccine doses and a documented anti-HBs serum antibody level ≥100 IU/l.8
With regards to varicella, anti-VZV-IgG serum antibody measurement (enzyme-linked immunosorbent assay) is offered to all unimmunized students with a varicella history other than “yes, certain”.
We used SPSS Statistics software version 22.0 (IBM Switzerland, Zurich, Switzerland) for statistical analysis. Independent proportions were compared by Fisher’s exact test or Pearson’s χ2 squared test as appropriate. If not indicated otherwise, continuous data are given as mean values (median; range). P < 0.05 was considered as statistically significant.
This data analysis was approved by the local multi-cantonal ethical committee in February 2014 (EKNZ 2014–037).
During 2011–2013, 133 medical students (101 females, 75.9%) were enrolled in elective periods in our hospital. Their mean age was 25.5 years (median: 25; interquartile range: 24–26, range: 22–49). Two students did not fill in the questionnaire and therefore were excluded from subsequent analysis. Eighty-seven students (65.4%) were from Switzerland, 30 (22.6%) students were from Germany, 7 (5.3%) students were from Austria, 2 (1.5%) students each were from Italy and Poland and 1 (0.8%) student each was from England, Hungary and Azerbaijan.
Varicella and Pertussis Disease History
A total of 120 students (91.6%) had a certain history of varicella. Four students (3.1%) probably had varicella, 1 of whom (0.8%) had been vaccinated against varicella. One student (0.8%) had a possible history of varicella, subsequently confirmed by us by VZV-IgG positivity. Two students could not recall having had varicella and both were seropositive for VZV-IgG by ELISA. Four students had a negative history of varicella: 2 of them were subsequently vaccinated against varicella by us and in the other 2 students previous VZV infection was confirmed serologically. In summary, all 131 students had evidence of varicella protection.
Eleven students (8.4%) had a positive history of pertussis. Two students (1.5%) probably had pertussis, 112 students (85.5%) stated they never had pertussis and 6 students (4.6%) were not able to give any information about a history of pertussis.
Documented immunization status against diphtheria, tetanus, poliomyelitis, pertussis, measles, mumps, rubella and HB as well as HBs antibody values are shown in Table 1. Documented immunization status was complete and up to date according to the Swiss national immunization guidelines in 29 students (22.1%) and 19 (14.5%) also had previously documented anti-HBs antibody values ≥100 IU/l.
All remaining 112 students required at least 1 intervention. There was a nonsignificant difference between Swiss and foreign students regarding complete immunization status, that is, 16 (18.4%) of 87 Swiss students were up to date compared with 13 (29.5%) of 44 foreign students (P = 0.146).
With regards to pertussis, 15 (43%) of 35 students, 17 (36%) of 47 students and 24 (49%) of 49 students in years 2011, 2012 and 2013, respectively, were up to date with their immunization status. We found significantly higher pertussis immunization rates concordant with current guidelines amongst German students (19 of 30; 63.3%) or all foreign students combined (26 of 44; 59.1%) compared with Swiss students (30 of 87; 34.5%; P = 0.006 and P = 0.007, respectively).
Of 131 students, 107 (81.7%) had a complete mumps immunization history by use of any MMR vaccine. However, when doses of Triviraten were excluded, only 89 (67.9 %; P = 0.01) were up to date for mumps immunization. Furthermore, we observed higher rates of complete immunization against rubella in female students (84.0%) compared with male students (67.7%; P = 0.047).
Medical students with patient contact are at risk for contracting and transmitting infectious diseases like all other healthcare personnel. Our ongoing surveillance program identifies significant immunization gaps among medical students in their final years of training with no improvement since our first evaluation a decade ago.6 The main reason for this shortcoming is the lack of a standardized immunization program for medical students at our university, despite repeated advocating for such a program by members of our group. In contrast, students visiting from foreign universities tend to have a higher rate of complete immunization status (29.5% vs. 18.4%; P = 0.146). This may not only be because of locally implemented immunization programs (information which we did not collect) but rather be explained by different general immunization recommendations in foreign countries. For example, pertussis vaccination for healthcare personnel caring for children <6 months of age has been recommended in Germany since 2003 (and for all healthcare personnel since 2009)9 but only since 2011 in Switzerland.8 This might explain the significantly lower immunity rates against pertussis among Swiss students compared with German students.
With respect to MMR, immunization gaps of 10% and higher are of particular concern. Consistent with our findings a decade ago,6 we observed a (nonsignificant) lower rate of complete immunization against rubella in males than females (67.7% vs. 84.0%). Although our study is restricted to medical students, this finding indicates that there is still a widely held misconception that rubella immunization is more important for females than for males and that strategies for catch-up MMR immunization in adults need to be intensified in general in Switzerland.
In conclusion, our ongoing surveillance program is identifying immunization gaps in medical students already well-advanced in their medical education. Intervention at an earlier stage of their medical career, that is, before first patient contact, is warranted and should be implemented by the medical faculty. It is our experience that medical students’ awareness of their immunization gaps is low and, in accordance with a different study, their willingness to accept immunizations is high.10 This observation strongly supports the implementation of catch-up immunization programs for first year medical students in the future.
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