Influenza Vaccination of Pregnant Women and Serious Adverse Events in the Offspring.

Publisher: MDPI Country of Publication: Switzerland NLM ID: 101238455 Publication Model: Electronic Cited Medium: Internet ISSN: 1660-4601 (Electronic) Linking ISSN: 16604601 NLM ISO Abbreviation: Int J Environ Res Public Health Subsets: MEDLINE

Original Publication: Basel : MDPI, c2004-

Pregnancy*; Influenza Vaccines/*adverse effects ; Vaccination/*adverse effects; Adult ; Fatty Acids, Omega-3 ; Female ; Health Status ; Humans ; Infant ; Infant Mortality ; Infant, Newborn ; Influenza, Human/prevention & control ; Observational Studies as Topic ; Pregnancy Complications, Infectious/prevention & control ; Pregnant Women ; Randomized Controlled Trials as Topic ; Risk

Pregnant women are increasingly considered a priority group for influenza vaccination, but the evidence in favor relies mainly on observational studies, subject to the "healthy-vaccinee bias". Propensity score methods-sometimes applied-reduce but cannot eliminate residual confounding. Meta-analyses of observational studies show relative risks far from the thresholds that would confirm the efficacy of universal vaccination for pregnant women without needing randomized controlled trials (RCTs). Critical articles have shown that in the four RCTs investigating the outcomes of this vaccination, there was a tendency towards higher offspring mortality. In the largest RCT, there was a significant excess of presumed/serious neonatal infections, and also significantly more serious adverse events. Many widely acknowledged observational results (about hormone replacing therapy, vitamin D, omega-3 fatty acids, etc.) were confuted by RCTs. Therefore the international drive to consider this vaccination a "standard of care" is not justified yet. Moreover, there is the risk of precluding further independent RCTs for "ethical considerations", so as "to not deny the benefits of influenza vaccinations to pregnant women of a control group". Instead, before promoting national campaigns for universal vaccination in pregnancy, further large, independent, and reassuring RCTs are needed, even braving challenging a current paradigm. Until then, influenza vaccination should be offered to pregnant women only once open information is available about the safety uncertainties, to allow truly informed choices, and promoting also other protective behaviors.

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Keywords: healthy-vaccinee bias; influenza vaccination; informed consent; offspring deaths; pregnant women; real-world vs. randomized evidence; serious adverse events increase

0 (Fatty Acids, Omega-3)
0 (Influenza Vaccines)

Date Created: 20191110 Date Completed: 20200323 Latest Revision: 20200323

20221213

PMC6887964

10.3390/ijerph16224347

31703366