The SearchVoat Forum

The use of mRNA vaccines in pregnancy is now generally considered safe for protection against
COVID-19 in countries such as New Zealand, USA, and Australia. However, the influential CDC-
sponsored article by Shimabukuro et al. (2021) used to support this idea, on closer inspection, provides
little assurance, particularly for those exposed in early pregnancy. The study presents falsely reassuring
statistics related to the risk of spontaneous abortion in early pregnancy, since the majority of women in
the calculation were exposed to the mRNA product after the outcome period was defined (20 weeks’
gestation).

In this article, we draw attention to these errors and recalculate the risk of this outcome based on the
cohort that was exposed to the vaccine before 20 weeks’ gestation. Our re-analysis indicates a
cumulative incidence of spontaneous abortion 7 to 8 times higher than the original authors’ results
(p < 0.001) and the typical average for pregnancy loss during this time period. In light of these findings,
key policy decisions have been made using unreliable and questionable data. We conclude that the
claims made using these data on the safety of exposure of women in early pregnancy to mRNA-based
vaccines to prevent COVID-19 are unwarranted and recommend that those policy decisions be
revisited.

The use of mRNA vaccines in pregnancy are
reported as being safe for pregnant women and their
unborn child(ren) for protection against COVID-
19, in countries such as New Zealand,[1] USA,[2]
and Australia.[3] However, the article by
Shimabukuro et al. (2021)[4] used to support this
idea, on closer inspection, provides little assurance,
particularly for women exposed in early pregnancy.
Here, we outline these concerns and question the
unrestricted use of these vaccines in pregnant women.

However, closer inspection of the 827 women in
the denominator of this calculation reveals that
between 700 to 713 women were exposed to the
vaccine after the timeframe for recording the
outcome had elapsed (up to 20 weeks of
pregnancy). Hence, a re-analysis of these figures
indicates a cumulative incidence of spontaneous
abortion ranging from 82% (104/127) to 91%
(104/114), 7–8 times higher than the original
authors’ results.

Transmission of mRNA and spike protein
The transmission of mRNA and spike protein
across the placenta and through breast milk is of
concern, given the unknown effect on development
in utero or on a breastfeeding infant. There were no
mRNA spike-encoding region amplifications
detected in aqueous or liquid breast milk fractions
0–7 days post-vaccination (n=5) in a study carried
out by Mattar et al. in 15 pregnant women and five
breast-feeding women who received one Pfizer-
BioNTech (BNT162B2) mRNA vaccination.[25]
However, the presence of spike protein itself was
not tested for. The authors of this study urge
caution, given the small sample sizes and study
duration of only one week post-exposure. In
contrast to this study, voluntary reporting systems
such as VAERS have received numerous reports of
thrombotic thrombocytopenic purpura (TTP),
gastrointestinal upset, rash, anaphylactic reaction
and death (for example, VAERS ID26: 1166062;
927664; 939409; 954010; 1166062; 1224688;
1254975; 1272428; 1343886; 1395088; 1415059;
1445743; 1031318; 1113464; 1182232) following exposure to breastmilk of a recently vaccinated
mother.

Conclusion

We question the conclusions of the Shimabukuro et
al.[4] study to support the use of the mRNA vaccine
in early pregnancy, which has now been hastily
incorporated into many international guidelines for
vaccine use, including in New Zealand.[1] The
assumption that exposure in the third trimester
cohort is representative of the effect of exposure
throughout pregnancy is questionable and ignores
past experience with drugs such as thalidomide.[38]
Evidence of safety of the product when used in the
first and second trimesters cannot be established
until these cohorts have been followed to at least the
perinatal period or long-term safety determined for
any of the babies born to mothers inoculated during
pregnancy. Additionally, the product’s manufacturer,
Pfizer, contradicts these assurances, stating:
“available data on Comirnaty administered to
pregnant women are insufficient to inform vaccine-
associated risks in pregnancy”, and “it is not known
whether Comirnaty is excreted in human milk” as
“data are not available to assess the effects of
Comirnaty on the breastfed infant” (page 14).[39]
Due to the nature of the mRNA vaccine roll-out,
healthcare providers need to report any issues in
pregnancy to further determine the safety of this
product. Caution should be exercised in the
administration of vaccines in pregnancy, as
indicated by the possible association between the
exposure to influenza vaccines containing
H1N1pdm09 (2010–11 and 2011–12) and
spontaneous abortion.[40] Considering the
evidence presented here, we suggest the immediate
withdrawal of mRNA vaccine use in pregnancy
(Category X)[41] and those breastfeeding,
alongside the withdrawal of mRNA vaccines to
children or those of child-bearing age in the
general population, until more convincing data
relating to the safety and long-term impacts on
fertility, pregnancy and reproduction are established in these groups.