Updated as of January 2021

Maven’s Medical Director Dr. Jane van Dis has been closely following results of vaccine studies and keeping our members, providers, and team updated with the latest clinical guidance for COVID-19 for women and families.

Here are FAQs on the vaccine answered by Dr. van Dis with all of the details she has gathered for pregnant women, as well as anyone looking for more information about the vaccine trials, specifics of the vaccine, side effects and effectiveness, who should get it, and more.

“I hope this is helpful as you speak with your family, friends, and others about the vaccine,” shares Dr. van Dis. 

The latest for pregnant women

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Should pregnant women get the COVID-19 vaccine? 

The American College of Obstetricians and Gynecologists (ACOG) released a statement on December 13th stating the following, among additional details: 

  • ACOG recommends that COVID-19 vaccines should not be withheld from pregnant individuals who meet criteria for vaccination based on CDC Advisory Committee on Immunization Practices (ACIP)-recommended priority groups. 
  • COVID-19 vaccines should be offered to lactating individuals similar to non-lactating individuals when they meet criteria for receipt of the vaccine based on prioritization groups outlined by the ACIP.
  • Individuals considering a COVID-19 vaccine should have access to available information about the safety and efficacy of the vaccine, including information about data that are not available. 

Among my peers, the overall consensus is that it would be unethical to withhold this vaccine from pregnant women.  Here’s an editorial about it and the process by which pregnant women were excluded from these trials to date.

Were pregnant patients included in the vaccine trials?  

No. However, the Society for Maternal Fetal Medicine released a statement on December 1, 2020 stating that they, “strongly recommend that pregnant women have access to COVID-19 vaccines in all phases of future vaccine campaigns, and that she and her healthcare professional engage in shared decision-making regarding her receipt of the vaccine.”  

What are the barriers to pregnant women receiving the COVID-19 vaccine? 

There should be no barriers to pregnant women receiving the COVID-19 vaccine if, after discussion with their health care provider, they meet criteria for vaccination based on ACIP-recommended priority groups.

Pregnant women already routinely receive many vaccines, such as the flu vaccine and the TDap vaccine, among others.

About the COVD mRNA vaccine

What happened with the COVID-19 vaccine on Thursday December 10, 2020? 

The vaccine that was discussed Thursday was the Pfizer vaccine, a mRNA vaccine, and the FDA vaccine advisory panel (a body not associated with the government nor the pharmaceutical companies) formally recommended the FDA authorize the vaccine. 

Tell me about the Pfizer vaccine?  

This vaccine is a 2-dose mRNA vaccine with an efficacy rate of 95% after two doses administered 3 weeks apart.  All COVID vaccines are required to go through randomized placebo controlled trials with tens of thousands of participants; the Pfizer vaccine trials had over 43,000 participants. Most common side effects after pain at the injection site recorded by Pfizer were fatigue and headache. The company is expected to make up to 50m doses in 2020 and 1.3b doses in 2021. The safety of the vaccine is monitored for at least 60 days after the 2nd dose before approval is sought. All but one of the COVID-19 vaccines currently in trials in the U.S. need 2 shots to be effective. 

Tell me about the Moderna vaccine

Data has shown that the vaccine has an efficacy rate of 94.1%. This vaccine requires two injections given 28 days apart.  Side effect information is below.

How are vaccines made? 

Vaccines are made by administering one of the following: 1) an inactive portion of a virus or an inactive portion of a bacterial toxin; 2) a weakened (live) portion of a virus; or 3) the genetic code (DNA, mRNA or vectored viruses) for part of the virus. The last example is how the Pfizer and Moderna COVID-19 vaccine was made. These vaccines contain “the blueprint” for producing antigens rather than the antigen itself. All provoke the body’s immune response to form antibodies against the virus in question. 

What is mRNA? Is it different from DNA? 

mRNA is “messenger” RNA. mRNA is the copy (a complementary sequence) that is made from DNA. Imagine that there is a scribe standing in front of your DNA molecule and the scribe writes down everything DNA says (that’s mRNA)… and then mRNA uses those notes to make a protein. It’s the messenger that takes the code from the DNA to the ribosomes, which are the cell’s protein factories. I saw someone else refer to mRNA as the Snapchat of molecules because it helps to create a protein, but breaks down quickly after that. 

How does a mRNA vaccine work? 

The mRNA vaccine is a snippet of the outside “spike protein” from the coronavirus, called an S Protein. Because the coronavirus is a mRNA virus, an engineered snippet mRNA gets coated in lipid (fat) and then injected into the deltoid muscle on your upper arm. Once inside your body, your immune system “reads” the information on the snippet. The vaccine tells your cell how to make the harmless piece of spike S protein, and then your cells start making the protein pieces.  Next, your immune system recognizes that the proteins don’t “belong” to you, and starts making antibodies to that spike protein. Interestingly, I read, “RNA vaccines are faster and cheaper to produce than traditional vaccines, and a RNA based vaccine is also safer for the patient, as they are not produced using infectious elements.” Importantly, this mRNA vaccine also doesn't enter the cell nucleus.


How did they calculate the effectiveness of preventing COVID after vaccination with the Pfizer vaccine?

  • Placebo → 162 persons from the 21,728 that received placebo vaccine got COVID
  • Vaccine → 8 persons from the 21,270 that received actual vaccine got COVID
  • 95% CI; 90.3 to 97.6

Did the researchers account for demographic differences within the populations they studied?

Yes, confounding variables they adjusted for included: age, sex, race, and comorbidities.

Side effects & limitations

Can the COVID vaccine give you COVID? 


What are some possible side effects of the vaccine?  

The most common side effect is always going to be pain and redness at the injection site.  Yes, from the needle, but also from the vaccine. Some people get a low-grade fever, muscle ache, headache, chills, joint pain or body aches, and side effects were reported with the Pfizer vaccine to be more frequent after the 2nd dose. 

From Pfizer:

Among those 18-55 years of age:

  • 16% had a fever after the second dose
  • 59% fatigue after 1st dose; 52% after second dose
  • 52% headache
  • 35% chills
  • 22% joint pain
  • 10% diarrhea
  • 83% pain at injection site after 1st dose; 78% after 2nd dose

Among those older than 55 years of age:

  • 71% pain at injection site after the first dose; 66% after the 2nd dose
  • 11% of those age > 55 had fever
  • 51% fatigue
  • 39% headache

Severe systemic events reported in < 2% of recipients of either dose.

From the Moderna trial:

  • 9.7% fatigue
  • 8.9% muscle aches
  • 5.2% joint pain
  • 4.5% headache

What are the severe adverse events reported in recipients of the Pfizer vaccine? 

  • 0.3% reported lymphadenopathy (swollen lymph nodes)
  • 4 out of the 21,720 who received vaccine reported adverse events
  • Shoulder injury related to vaccine administration
  • Right axillary lymphadenopathy
  • Ventricular arrhythmia
  • Right leg paresthesia 
  • 2 vaccine recipients died 
  • 1 from arteriosclerosis
  • 1 from cardiac arrest
  • 4 placebo recipients died
  • 2 from unknown
  • 1 from hemorrhagic stroke
  • 1 from heart attack
  • Importantly, NO DEATHS were considered by investigators to be related to the vaccine or placebo
  • Safety monitoring will continue for 2 years after administration of the 2nd dose of vaccine

What’s the ability of the study to detect adverse effects?

  • This study has > 83% probability of detecting at least one adverse event if the incidence is presumed to be 0.01%
  • This study is not large enough to detect less common adverse events; for instance, events that happen in only 1 out of 50,000 or 100,000 persons
  • All participants were studied for a minimum of 2 months, but some were studied for 3 ½ months
  • Investigators will continue to monitor adverse events for at least 2 years

What are the limitations of these vaccine studies? 

  • No younger adolescents, children and pregnant women were studied 
  • Safety and immune response date from adolescents 12-15 will be reported subsequently, as well as data in children and pregnant women and immunocompromised individuals
  • The Pfizer vaccine can be stored for up to 5 days at standard refrigerated temperatures
  • Very cold temperatures are required for shipping and storage  

When should I worry about side effects? 

If you have a reaction such as a fever that lasts longer than 3 days, or if you have a serious side effect that prevents you from eating, sleeping or regular daily activities. Importantly, in previous vaccine launches, nearly all serious side effects were witnessed within the first 60 days of vaccine administration, and for these vaccines, the trials started July 27, nearly 5 months ago. 

Who should get the vaccine

Should people who had COVID get the vaccine? 

The CDC Advisory Committee on Immunization Practices (ACIP) recommends that all individuals should be vaccinated regardless of whether they have had COVID previously. Importantly, the vaccine trials did include individuals who had been previously infected. They suggest that the vaccine will provide stronger immunity than natural immunity (immunity from having COVID); and we have seen rates of reinfection, so definitely recommend getting vaccinated even if you had COVID.  

Will children be able to get COVID vaccine? 

Some of the trials include children over the age of 12. Dr. Fauci said that trials with children and pregnant women will begin in January.


Dr. Jane van Dis is Maven’s Medical Director, a board-certified OB-GYN, and a frequent writer and speaker about gender equity in medicine. On our blog, Dr. van Dis shares insights on improving outcomes during pregnancy and beyond, as well as the latest clinical guidance in women’s and family health. Follow her @JanevanDis.

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