1.5.2.2 Side effects and safety of vaccination

Because a vaccine contains weakened or inactivated bacteria or viruses and adjuvants that do not occur naturally in the body, vaccination can have side effects. Common side effects include redness at the injection site (>10% of cases), fever, headache, swelling of a limb where the vaccine was injected (1-10% of cases) and crying in babies. In addition, allergic reactions such as skin rashes all over the body and itching may occur. There are also specific side effects of certain vaccinations. For example, after MMR (mumps, measles, rubella) vaccination, a temporary deficiency of platelets occurs in 1:20000 children.

On the occurrence of very severe allergic reactions and side effects, such as anaphylactic shock, breathing difficulties or even death, there is a difference of opinion in the Netherlands. The Lareb side effects centre reports annually on side effects of vaccinations. [8: Bijwerkingencentrum Lareb. Meldingen van bijwerkingen Rijksvaccinatie-programma. Jaarlijkse rapportages. 2011-2018 www.lareb.nl.] More serious events, which are seen on websites of, for example, the Nederlandse Vereniging Kritisch Prikken (NVKP; Dutch Association for Critical Prickings) as adverse reactions to vaccinations, have not been reported to Lareb or, according to Lareb, cannot reasonably be considered to be due to the administration of the vaccine.

One topic of debate is whether autism could be a complication of MMR vaccination. There has been confusion about this in the recent past. The journal The Lancet published a study in 1998 linking the MMR vaccine with the incidence of nonspecific colitis and autism. [9: A.J. Wakefield, S.H. Murch, A. Anthony, J. Linnell, D.M. Casson, M. Malik, M. Berelowitz, A.P. Dhillon, M.A. Thomson, P. Harvey, A. Valentine, S.E. Davies and J.A. Walker-Smith. Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children. Lancet. 1998/03/21 ed 1998, 351, 637-641 doi:10.1016/s0140-6736(97)11096-0.] In the UK, MMR vaccination coverage dropped remarkably after this publication. The Lancet retracted the article in 2010 due to conflict of interest and fraud by authors. [10: C. Dyer. Lancet retracts Wakefield’s MMR paper. BMJ. 2010/02/04 ed 2010, 340, c696 doi:10.1136/bmj.c696 https://www.ncbi.nlm.nih.gov/pubmed/20124366.] Another study linking MMR vaccination and autism was also retracted by a journal due to unsound methodology. [11: B.S. Hooker. Measles-mumps-rubella vaccination timing and autism among young African American boys: a reanalysis of CDC data. Transl Neurodegener. 2014/08/13 ed 2014, 3, 16 doi:10.1186/2047-9158-3-16.] [12: B.S. Hooker. Retraction: Measles-mumps-rubella vaccination timing and autism among young African American boys: a reanalysis of CDC data. Transl Neurodegener 2014, 3, 22.] On its website, however, the NVKP endorses the conclusions of the retracted article in The Lancet and accuses those who want to prove that there is no link between MMR and autism of conflict of interest and fraud. It goes on to cite an epidemiological study purporting to show that the incidence of autism among people born from 1998 onwards, the year in which the MMR vaccination rate fell as a result of the above-mentioned publication in The Lancet, was much lower than before, and then gradually rose again among people born from 2000 onwards. [13: T.A. Deisher, N.V. Doan, K. Koyama and S. Bwabye. Epidemiologic and Molecular Relationship Between Vaccine Manufacture and Autism Spectrum Disorder Prevalence. Issues Law Med 2015, 30, 47-70.] Such an observation is certainly striking, but not evidence of a causal relationship between MMR vaccination and autism. In any case, what this discussion shows is that there is an ongoing uncertainty with regard to interpreting and weighing results of scientific research and that the objectivity of scientists’ conclusions, even when they enjoy a good reputation as such, is not beyond doubt.

The (alleged) side effects are mainly a reason for group of highly educated people to oppose vaccination. The first and most important reason for them is the lack of sense of urgency, due to the fact that, as a result of the long-term high vaccination coverage, outbreaks of certain diseases have hardly occurred in the Netherlands for a long time. But secondly, paradoxically, it probably also plays a role that precisely highly educated people will delve into the side effects that might exist, question the information about vaccination provided by government bodies and researchers, and interpret the available data – rightly or wrongly – differently from scientists.

Side effects of the vaccines have also been reported in the extensive vaccination programmes against SARS-CoV-2. In general, these were mild side effects, such as short-term malaise, fever or pain in the arm where the injection was given. Rare but serious side effects also appeared to occur: the Astra-Zeneca vaccine and (to a lesser extent) the Janssen vaccine have been associated with thrombosis with thrombocytopenia syndrome, a condition in which both thrombosis and a low platelet count are observed. The Pfizer vaccine is associated with myocarditis (inflammation of the heart muscle).