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Covid-19 Vaccination in Pregnancy

Posted by Professor Mike O’Connor AM on 15 June 2021
Covid-19 Vaccination in Pregnancy

The RANZCOG and ATAGI recommend that pregnant women are routinely offered Pfizer mRNA vaccine (Cominarty) at any stage of pregnancy. This is because the risk of severe outcomes from COVID-19 is significantly higher for pregnant women and their unborn baby. (9 June 2021)

High risk women include those who:

  1. Are immunosuppressed
  2. Recent bone marrow transplant
  3. Graft versus host disease
  4. Leukaemia, lymphoma,
  5. Myelodysplastic syndrome
  6. Chemotherapy or radiotherapy
  7. Occupations at high risk of exposure

Moderate risk women include those with:

  1. Diabetes
  2. Severe asthma
  3. Heart disease
  4. Chronic renal or liver disease
  5. Obesity (BMI>40)
  6. Chronic inflammatory conditions

There is no contraindication to vaccinating women who are breastfeeding.

What are the risks of COVID-19 acquired during pregnancy?

There is sufficient data now to link Covid-19 infections during pregnancy to an increased risk of:

  1. Severe maternal respiratory illness that results in ICU admission, mechanical ventilation, and deathcompared with non-pregnant people.

    The relative risk for Asian  women was 6.6:1 and for  South  Pacific Islanders (RR  3.7:1)

Although the absolute risks of serious outcomes for pregnant women were low, they were at increased risk for severe COVID-19 disease, possibly because of physiologic changes in pregnancy, including increased heart rate and oxygen consumption, reduced lung capacity, a shift away from cell-mediated immunity, and elevated risk of blood clots.

  1. Preterm delivery: Rate 12.9% vs 10.2% controls with 1/4 babies admitted to neonatal care unit

    Of 16 babies which were COVID-19 positive at birth, half were born before 37 weeks gestation.

Reducing the Rate of Preterm Delivery by Public Health Prevention

There is evidence from Denmark and the Republic of Ireland that public health measures implemented to reduce transmission of COVID 19 have resulted in reduced rates of prematurity. For example the rate of deliveries before 28 weeks was reduced from 2.19 (in 2015 to 2019) to 0.19 per 1000 births in Denmark in 2020. In Ireland the incidence of babies with birthweights below 1500 g dropped from 8.18  (from 2001 to 2019) to 2.17 per 1000 births in 2020.

Covid-19 vaccination during pregnancy

Is the rate of miscarriage increased in Covid 19 pregnancies? No

The frequency of miscarriage does not appear to be increased, but data on first- and second-trimester infections are limited.

Vertical transmission of COVID19 virus: Yes

There is potential transmission of Covid-19  to baby with an estimated rate of transmission = 2.9%.

Is there an increased risk of fetal anomalies in Covid-19 pregnancies? No

An increased risk for congenital anomalies has not been reported.

Should pregnancies be delayed after Covid-vaccination? No

Currently available vaccines for prevention of COVID-19 are not thought to affect fertility, pregnancy testing is not a requirement prior to receiving any approved COVID-19 vaccine, and it is not necessary to delay pregnancy after vaccination.

The RCOG stated on 9 April 2021 that the extremely low risk of thrombosis and thrombocytopoenia with the Astra Zenica vaccine  following vaccination and caused by rogue antibodies to platelet factor 4 is not directly linked to increased prothrombotic risks. Although younger women who are pregnant, recently postnatal, or on fertility treatment are all at increased thrombotic risk, the lack of a clear direct association between a thrombotic risk and the likelihood of this extremely rare adverse event should be considered.

How effective are Covid-19 vaccines?

  • Pfizer95percent efficacy in preventing an infection in people with no prior infections.
  • Moderna94.1 percent effective at preventing a symptomatic infection in people who have not previously contracted a coronavirus infection.
  • Johnson & Johnson72 percent overall efficacy and 86 percent efficacy against severe illness.
  • AstraZeneca: 76 percent effective at reducing the risk of symptomatic disease after both doses, and 100 percent effective against severe disease.

Logistics of Astra Zenica and Pfizer vaccines

  1. The Oxford Astra Zenica vaccine can be stored at minus 4 degrees Celsius. The dose is 0.5 mls IMI with a second dose given 12 weeks later. Most Australians will receive this vaccine.
  2. Pfizer-BioNTech COVID-19 vaccine must be stored at minus 70 degrees Celsius The mRNA in Pfizer is very unstable at higher temperatures notwithstanding its stabilised nucleosides and lipid coating: the recommended dose is 0.3 mls IMI which is repeated in 3 weeks.

The COVID-19 vaccine by Pfizer is preferred over COVID-19 Vaccine AstraZeneca in adults aged under 50 years. This recommendation is based on a potentially increased risk of thrombosis with thrombocytopenia following AstraZeneca vaccine in those under 50 years. Thrombosis with Thrombocytopenia Syndrome (TTS) is a rare and new syndrome which involves blood clots (occurring in body sites like the brain or abdomen) together with low platelet levels. The rate of TTS is 20-40 cases per million.

Further Reading: 

  1. Centre for Infectious Disease Research & Policy Studies  Risk of preterm birth, severe COVID-19 in pregnant women November 03,2020
  2. Woodworth KR, Olsen EO, Neelam V, et al. Birth and Infant Outcomes Following Laboratory-Confirmed SARS-CoV-2 Infection in Pregnancy - SET-NET, 16 Jurisdictions, March 29-October 14, 2020. MMWR Morb Mortal Wkly Rep 2020; 69:1635.
  3. Berghella V,Hughes B Covid 19-Pregnancy issues and antenatal care. UpToDate March 26,2021
  4. Voysey  M et al Single-dose administration and the influence of the timing of the booster dose on immunogenicity and efficacy of ChAdOx1 nCoV-19 (AZD1222) vaccine: a pooled analysis of four randomised trials Lancet  2021 397 (10277):881-891
Author:Professor Mike O’Connor AM

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