Inadequate Pregnancy Vaccine studies and Why

Share and help others

After publishing Vaccinations in Pregnancy some people posted links to studies that they felt showed vaccines to have been tested for safety in pregnant women.

It is important to remember that no vaccine has ever been proven to be safe. This is because none have ever passed the “gold standard” of testing for drugs, the double-blind, placebo controlled study. To do this the vaccine would need to be tested against a control group that has never received a vaccine ever in their lives and this has never been done. So even before we look at the following selection of studies we can see that it is not possible to claim that vaccines are safe for pregnant women to receive.

The following are a selection of the studies that people refer to as showing that giving vaccines in pregnancy is safe for both the mother and child. After each study I have listed why the study does not prove safety. Most do not even look look for miscarriages, fetal (baby) death, fetal (baby) developmental issues or maternal (mother) death. In the main these studies are retrospective observational cohort studies. This means that a group of people sharing a common exposure factor (vaccine) were historically looked at (followed after having been given the vaccine). So these studies observe women who have already been given a vaccine during pregnancy which has not been proven to be safe for them to receive. It is interesting to note that observational studies of pregnant women and vaccines are deemed acceptable by the medical establishment, while the observations of parents that their children’s health changed following a vaccine is not acceptable. Both are retrospective, observational and follow a cohort group.

1. Maternal safety of trivalent inactivated influenza vaccine in pregnant women. Nordin JD, Kharbanda EO, Benitez GV, Nichol K, Lipkind H, Naleway A, Lee GM, Hambidge S, Shi W, Olsen A. PMID:23635613

  1. This is a retrospective observational cohort study. This is not a trial done prior to the release of the vaccine to establish its safety during pregnancy.
  2. The study only follows the women for 42 days after receiving the vaccine. This is not long enough to determine if there has been long term damage such as fertility issues. It is not long enough to establish if there are long term issues in the development of the child.
  3. It is only looking at issues in the first trimester of pregnancy. In the first 3 days after receiving the vaccine it was not associated with an increase in the following specified events, allergic reactions, cellulitis, and seizures in the women; and in the first 42 days, no incident cases of Guillain-Barré syndrome, optic neuritis, transverse myelitis, or Bells palsy were identified. However we do not know what happened after this time period.
  4. This study does not look at whether their were miscarriages, fetal deaths, maternal deaths or hospitalisations. It does not follow up long term and is only looking at a very narrow range of health issues.


2. Adverse events following administration to pregnant women of influenza A (H1N1) 2009 monovalent vaccine reported to the Vaccine Adverse Event Reporting System – Pedro L. Moro, MD, MPH; Karen Broder, MD; Yenlik Zheteyeva, MD, MPH; Natalya Revzina, MD; Naomi Tepper, MD, MPH; Dmitry Kissin, MD, MPH; Faith Barash, MD, MPH; Jorge Arana, MD, MPH; Mary D. Brantley, MPH; Helen Ding, MD, MSPH; James A. Singleton, MS; Kimp Walton, MS; Penina Haber, MPH; Paige Lewis, MSPH; Xin Yue, MS; Frank DeStefano, MD, MPH; Claudia Vellozzi, MD, MPH

  1. Again this is not a pre-approval for use safety study. It is a review of adverse events reported to the Vaccine Adverse Event Reporting System (VAERS). The first issue here is that it is generally agreed that only 1-10% of adverse events are reported.
  2. Out of 294 reports looked at – an extremely small number – 2 women died, 59 women were hospitalised, 95 women had spontaneous abortions, 18 women had still births, 7 women delivered preterm, 3 women had threatened abortions, 2 women had preterm labors, 2 women had preeclampsia, 1 baby had hydronephrosis (swelling of kidney due to retention of fluid), 1 baby had tachycardia (abnormally fast heartbeat), 1 baby had intrauterine growth retardation (failure to grow as expected in the womb), and 1 baby had a cleft lip.
  3. Despite all the above reported adverse events the study stated that it “did not identify any concerning patterns of maternal or fetal outcomes”.


3. Inactivated Influenza Vaccine During Pregnancy and Risks for Adverse Obstetric Events – Kharbanda, Elyse Olshen MD, MPH; Vazquez-Benitez, Gabriela PhD; Lipkind, Heather MD, MPH; Naleway, Allison PhD; Lee, Grace MD, MPH; Nordin, James D. MD, MPH; for the Vaccine Safety Datalink Team

  1.  Again this is not a pre-approval for use safety study. It is a retrospective observational cohort study.
  2. The women were only observed for 42 days.
  3. Only 13 health conditions were looked for – hyperemesis (severe nausea and vomiting such that weight loss can occur), chronic hypertension, gestational hypertension, gestational diabetes, proteinuria, urinary tract infection, preeclampsia or eclampsia, chorioamnionitis (intra-amniotic infection), puerperal infection, venous complications, pulmonary embolism, or peripartum cardiomyopathy. Notably spontaneous abortions, fetal death, maternal death, hospitalisations were not looked for. There were no long term follow ups.


4. Trivalent inactivated influenza vaccine and spontaneous abortion – Irving SA, Kieke BA, Donahue JG, Mascola MA, Baggs J, DeStefano F, Cheetham TC, Jackson LA, Naleway AL, Glanz JM, Nordin JD, Belongia EA; Vaccine Safety Datalink.

  1. This study does not tell us what kind it was but it would appear to be a retrospective study.
  2. Only abortions between 5-16 weeks of gestation were looked at. While no statistical increase in abortions was noted to be associated with the influenza vaccine, this does not look at the whole pregnancy period and 5-16 weeks during gestation is known to be a high risk time for abortions in pregnancy normally.
  3. The study size was extremely small 243 women.


5. Maternal Influenza Vaccine and Risks for Preterm or Small for Gestational Age Birth – James D. Nordin, MD, MPH; Elyse Olshen Kharbanda, MD, MPH; Gabriela Vazquez Benitez, PhD; Heather Lipkind, MD, MS; Claudia Vellozzi, MD, MPH; Frank DeStefano, MD, MPH on behalf of the Vaccine Safety Datalink

  1.  This is not a pre-approval for use vaccine safety study. It is a retrospective observational cohort study.
  2. It is only looking for two conditions, whether babies were born preterm or were of small size for their gestational age at birth. Nothing else.


6. Pregnancy Dose Tdap and Postpartum Cocooning to Prevent Infant Pertussis: A Decision Analysis – Andrew Terranella, Garrett R. Beeler Asay, Mark L. Messonnier, Thomas A. Clark, Jennifer L. Liang

  1. Again this is not a pre-approval for use vaccine safety study. It is a cohort model that simulates the cost effectiveness of giving vaccines.


7.  Immune Responses in Infants Whose Mothers Received Tdap Vaccine During Pregnancy – Hardy-Fairbanks, Abbey J. MD; Pan, Stephanie J. BS; Decker, Michael D. MD, MPH; Johnson, David R. MD, MPH; Greenberg, David P. MD; Kirkland, Kathryn B. MD; Talbot, Elizabeth A. MD; Bernstein, Henry H. DO, MHCM The Pediatric Infectious Disease Journal, November 2013, Vol. 32 – Issue 11: p 1257–1260

  1. Again not a pre-approval for use vaccine safety study. It is a retrospective cohort study.
  2. The following were excluded – women expecting more than one baby eg twins, serious underlying health issues in either mother or infant, preterm infants, and infants needing transfusions or advised not to have blood draws for health reasons. In real life Tetanus, Diphtheria and Pertussis do not avoid the excluded group.
  3. The study was based on collecting blood samples from the umbilical cord and only 5 women who had received the Tdap during pregnancy were tested.


8. Safety and Immunogenicity of Tetanus Diphtheria and Acellular Pertussis (Tdap) Immunization During Pregnancy in Mothers and Infants – A Randomized Clinical Trial Flor M. Munoz, MD; Nanette H. Bond, PAC; Maurizio Maccato, MD; et al; JAMA. 2014;311(17):1760-1769. doi:10.1001/jama.2014.3633

  1. While this study states that it is a double-blind, placebo controlled test, remember that the control group will have received vaccines at different stages in their lives and so are not “placebo” as it is not known what the long term effects of vaccines are on fertility or DNA.
  2. It only has 48 women in it.
  3. It excluded women who had an underlying chronic medical condition, were having more than one baby eg twins, and had a prenatal evaluation that predicted a complicated pregnancy. The women had to have normal first or second trimester screening test results.
  4. Primary outcomes were maternal and infant adverse events, pertussis illness, and infant growth and development until age 13 months. However it does not list what “adverse events” were considered. It does say “Whether an adverse event was attributable to vaccination was judged by the investigators considering temporality, biologic plausibility, and identification of alternative etiologies for each event” – so the investigators got to pick and choose what they considered to be an adverse event.
  5. Serious adverse events were reported by 22 of the participants however the investigators deemed them not attributable to the vaccine.


9. Maternal Influenza Vaccine and Risks for Preterm or Small for Gestational Age Birth – James D. Nordin, MD, MPH, Elyse Olshen Kharbanda, MD, MPH, Gabriela Vazquez Benitez, PhD, Heather Lipkind, MD, MS, Claudia Vellozzi, MD, MPH, Frank DeStefano, MD, MPH on behalf of the Vaccine Safety Datalink; The Journal of Pediatrics May 2014Volume 164, Issue 5, Pages 1051–1057.e2

  1. This is again a retrospective observational cohort study.
  2. It only looked for two things  rates of preterm delivery and small for gestational age (SGA) births.


It is important to always check studies. As can be seen from the second study listed above, if we only looked at the conclusion or abstract we would miss that the study did not take into account any of the adverse events reported. Always do your own research and base your decision on that and not on anyone else’s opinion. As always the above is for educational purposes and is not intended as medical advice.

Share and help others