The author provides insight into the most common problems that arise in everyday practice regarding vaccinations. Topics include immunological safety in the case of incomplete or distant and therefore forgotten vaccination series, the use of combination vaccinations, titer determination after hepatitis B vaccination, as well as questions about HPV vaccination in girls during puberty and MMR vaccination in pregnant women.
1. my patient was vaccinated against TBE twice a few years ago. Unfortunately, however, the third vaccination was forgotten, so that the immunization remained incomplete. Now that a few years have passed, do I have to start the vaccination series all over again?
Answer: No. The immunological memory remembers the vaccinations administered earlier. Thus, you can continue the started vaccination series where it was interrupted, even if a long time has passed since the last vaccination dose. Or, to put it another way, there are minimum intervals between doses in a vaccination series, but no maximum intervals. This principle applies to all vaccinations.
2. which vaccinations can I administer at the same time, and for which vaccinations is a minimum interval necessary?
Answer: In principle, all vaccines – whether live virus or inactivated – can be administered at the same time, but not in the same syringe and not at the same injection site. If you do not want to administer the vaccinations all at the same time, then a minimum interval (1 month) should be observed in only one situation: two live virus vaccinations (e.g., MMR and yellow fever). Two live virus vaccinations can be administered either simultaneously or then with a minimum interval of one month. This particularity is important and to be considered especially in case of travel medicine indication, when the yellow fever vaccination (together with the MMR) has to be done at the travel medicine doctor.
3. my patient was vaccinated only against measles as a child, now she wants to catch up on the vaccinations against rubella and mumps. However, it appears that monovalent vaccines against rubella and mumps are not available. What can I do in this situation?
Answer: You can use an MMR vaccine without any problems, even if not all three components would actually be needed, because the live attenuated viruses contained in the MMR vaccine are neutralized immediately if antibodies against the corresponding component(s) of the vaccine are already present. For this reason, overvaccination, such as with tetanus, does not occur with live virus vaccines.
4. my new practice assistant was already vaccinated against hepatitis B as a child, but no titer determination was carried out at that time. When I wanted to make up this determination now to determine her immunity, the anti-HBs titer was <5 mU/ml. What should I do now? Again a whole hepatitis B vaccination series and then titer determination again?
Answer: The negative titer in your practice assistant does not necessarily mean that she is not protected against hepatitis B, because anti-HBs titers drop continuously after vaccination and are no longer detectable sooner or later (depending on the initial titer). Nevertheless, cellular immunity (memory cells) exists in most vaccinated individuals, conferring lasting protection, provided the vaccinated individual has demonstrated an anti-HBs titer greater than 100 mU/ml one to two months after vaccination. Since this was not determined in your practice assistant at that time, you should now administer a single hepatitis B dose that boosts cellular immunity, resulting in a strong anti-HBs titer increase. You can then measure this one month later: Anti-HBs >100 mU/ml = lifelong protection.
5. one of my adult patients does not remember if, how often and against what he was vaccinated as a child. Do I now have to administer a full series of vaccinations with all recommended vaccines, even though my patient was probably vaccinated as a child?
Answer: If you can assume that your patient has been vaccinated previously, then it is worthwhile to vaccinate a single dose of dTpa (Boostrix®) and hepatitis B vaccine and determine the titers against tetanus and hepatitis B one month later. If the tetanus titer is above 500-1000 IU/l and the hepatitis B titer is above 100 mU/ml, then you have refreshed immunity with these individual vaccinations. If the titers are below this, further doses (basic immunization) must be administered.
6. one of my patients has an unmeasurable anti-HBs antibody titer despite having received three hepatitis B vaccinations. What do I have to do now?
Answer: What you should do first in this situation is to rule out chronic (asymptomatic) hepatitis B, as these patients typically do not (cannot) respond to hepatitis B vaccination: Determine anti-HBc antibody and HBs antigen positive for chronic hepatitis B. If you have ruled out chronic hepatitis B, then your patient is a hypo- or non-responder. In these patients, it is recommended that a second hepatitis B vaccination series (3 doses) be administered and then a titer determination be performed again. If the anti-HBs titer is then still negative, then your patient is a non-responder and must be advised that they are not protected in the event of exposure and therefore must be passively immunized after exposure. If the anti-HBs titer is positive but below 100 mU/ml, the patient is a hyporesponder who is protected only as long as an anti-HBs titer is measurable. In these patients, further hepatitis B vaccine doses usually result in a titer above 100 mU/ml, which correlates with long-term protection. Some experts recommend using the Twinrix® HepA/HepB combination vaccine for the second series of vaccinations, as it appears to be slightly more immunogenic than the monovalent hepatitis B vaccines alone.
7. I have heard that one should serologically confirm the vaccination success after hepatitis B vaccination. However, I have never done that until now.
Answer: Titer determination after vaccination is only necessary if the patient has an individual indication for hepatitis B vaccination (e.g. newborns of HBs-positive mothers, patients with familial, occupational or other exposure risk). After general vaccination, which is primarily recommended for adolescents in Switzerland, an anti-HBs titer determination is not indicated.
8. HPV vaccination has recently been recommended in Switzerland for girls aged 11-14 years with a 2-dose schedule, and for older girls with a 3-dose schedule. Now, which regimen applies to an adolescent who is still under 15 years of age at the first dose but over 15 at the second or third vaccination, respectively? A similar situation exists with hepatitis B vaccination, where a 2-dose schedule is recommended at age 11-15 years, followed by a 3-dose schedule.
Answer: The decisive factor for the choice of regimen is always the age at the first dose. This means that even with delayed administration of subsequent doses, a 2-dose schedule can be used if the vaccinated person was between 11 and 14 years of age (HPV) or 11 and 15 years of age (hepatitis B) at the first dose.
9. How long should contraception be maintained after MMR vaccination in a woman of childbearing potential to avoid potential infection of the child with the vaccine viruses? How dangerous is it if after MMR vaccination it turns out that the woman was pregnant at the time of vaccination?
Answer: Due to the (purely) theoretical risk of vaccine embryopathy, it is recommended to avoid pregnancy during one month. After that, vaccination viremia is no longer to be expected – and accordingly, there is no longer any risk of infection for the child. For reassurance, however, it may be said that there are now thousands of case reports where MMR was unintentionally administered during pregnancy. Embryopathies were not observed after MMR vaccination, so no measures are required in this situation, especially no interruptio.
10. Who can I contact if I have a specific question about vaccinations?
Answer: With the support of the FOPH, the Swiss Society of Pediatrics, the Swiss Society of Infectiology, the Swiss Society of Allergology and Immunology, and the University of Geneva, InfoVac (www.infovac.ch) operates an expert system that competently responds to e-mail inquiries from the medical profession about vaccinations and their correct use within 48 hours. In addition, InfoVac publishes a bulletin ten times a year with up-to-date vaccination information. For a contribution towards expenses of Fr. 25.- per year (Fr. 50.- for 2 years) you can actively participate in this system. Sign up at: www.infovac.ch.
Daniel Desgrandchamps, M.D.
HAUSARZT PRAXIS 2013; 8 (10): 21-23
