Abstract
Military personnel of all armed forces receive multiple vaccinations and have been doing so since long ago, but relatively few studies have investigated the possible negative or positive interference of simultaneous vaccinations. As a contribution to fill this gap, we analyzed the response to the live trivalent measles/mumps/rubella (MMR), the inactivated hepatitis A virus (HAV), the inactivated trivalent polio, and the trivalent subunits influenza vaccines in two cohorts of Italian military personnel. The first cohort was represented by 108 students from military schools and the second by 72 soldiers engaged in a nine-month mission abroad. MMR and HAV vaccines had never been administered before, whereas inactivated polio was administered to adults primed at infancy with a live trivalent oral polio vaccine. Accordingly, nearly all subjects had baseline antibodies to polio types 1 and 3, but unexpectedly, anti-measles/-mumps/-rubella antibodies were present in 82%, 82%, and 73.5% of subjects, respectively (43% for all of the antigens). Finally, anti-HAV antibodies were detectable in 14% and anti-influenza (H1/H3/B) in 18% of the study population. At mine months post-vaccination, 92% of subjects had protective antibody levels for all MMR antigens, 96% for HAV, 69% for the three influenza antigens, and 100% for polio types 1 and 3. An inverse relationship between baseline and post-vaccination antibody levels was noticed with all the vaccines. An excellent vaccine immunogenicity, a calculated long antibody persistence, and apparent lack of vaccine interference were observed.
Highlights
The military are exposed to infectious diseases as a consequence of their lifestyle with close inter-individual contacts and operational activity [1]
Based on blood samples’ availability at the three times (T0, T1, and T2), 49 subjects for MMR vaccine, 8 for varicella, and 56 for hepatitis A virus (HAV) were studied in group 1; the response to polio types 1 and 3 was explored in 52 subjects, distributed between the two groups, and the response to influenza was studied in 72 subjects, all belonging to group 2
The current study confirms the immunogenicity of MMR, varicella, polio, HAV, and influenza vaccines in healthy adults, with an apparent lack of reciprocal interference, especially for polio, HAV, and influenza, and demonstrates that the inverse association between baseline antibody values and the level of immune response observed for bacterial antigens such as meningococcal [27], pneumococcal [71] and tetanus/diphtheria [28] is detected for inactivated and live viral vaccines
Summary
The military are exposed to infectious diseases as a consequence of their lifestyle with close inter-individual contacts and operational activity [1]. Relatively few studies have faced the possible reciprocal negative or positive interference of simultaneous vaccines in adults [4]. Simultaneous inoculation of multiple antigens, including combined vaccines, is nowadays a routine practice in children, but the development of combined vaccines is generally preceded by long and accurate studies demonstrating safety and efficacy and aimed at preventing the reduction in immunogenicity as a consequence of antigens’. Studies in children receiving multiple vaccines demonstrated the possibility of reduced antibody response caused by antigen interference [7,8,9]. A possible positive interference has been recently reported in the US military [4], suggesting that the study of adults undergoing multiple, simultaneous vaccinations represents a valuable model to test this issue
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