Cedars-Sinai Blog

COVID-19 Vaccine: What Women Need to Know

A worried women getting her Covid-19 vaccine.

While it's clear COVID-19 vaccination protects you from an evolving virus—and far outweighs any side effects of the vaccines—health experts worry lingering fear and misinformation are keeping some women from being fully vaccinated. 

The Centers for Disease Control and Prevention (CDC) recommend most adult women receive a two-shot primary series of either the Pfizer-BioNTech or Moderna mRNA COVID-19 vaccines, followed by a booster dose at least five months after the last primary dose. 

The Johnson & Johnson (Janssen) shot is also approved as an alternative to the mRNA vaccines for some women. The CDC recommends these women receive a single primary dose of the Johnson & Johnson vaccine followed by a booster dose at least two months after the primary dose.

Cedars-Sinai women's health providers clear up what women should know about getting vaccinated.

COVID-19 vaccines work

Left unchecked, COVID-19 can trigger major health problems, including respiratory distress, cardiac events such as stroke, and even death. The approved COVID-19 vaccines are the most effective form of prevention, according to the CDC. 

Staying up to date with your COVID-19 vaccines—including getting your booster doses when eligible—keeps you safe against SARS-CoV-2 (the virus that causes COVID-19) and its recent variants, including Delta and Omicron. 

If you do develop a breakthrough infection after vaccination, you are still much less likely to become seriously ill, require hospitalization or die than if you were not vaccinated, the CDC says.

Get vaccinated even if you've already had COVID-19

As the pandemic wears on, many people will eventually contract SARS-CoV-2, the virus that causes COVID-19.

An infection does offer some cover—known as natural immunity—against a future case, the CDC notes. But experts caution this protection isn't reliable and can depend on your age, how long it's been since you were infected and how sick you were. Also, you still can pass on the virus and remain vulnerable to chronic symptoms.

It's safer to get vaccinated, which provides consistent, robust protection against the virus. Vaccination can also bolster existing immunity after natural infection, research shows.

Those who don't get vaccinated after having SARS-CoV-2 have more than two times the chance of getting it again than those who completed a full vaccine series after infection, according to the same study.

Vaccination doesn't affect fertility

The CDC recommends COVID-19 vaccination and boosters for pregnant and breastfeeding women, as well as for women who are trying to become pregnant or who might become pregnant in the future.

The CDC points to a growing body of evidence supporting the vaccines' safety in this vulnerable population, including:

  • No effect on chances of pregnancy in more than 2,000 women ages 21 to 45 
  • No link with preterm birth or underdevelopment at birth in a study of more than 40,000 pregnant women
  • No miscarriage risk among women who received mRNA vaccines (Pfizer-BioNTech and Moderna) just before and up to 20 weeks into pregnancy
  • No safety concerns reported on three vaccine-monitoring systems among infants or mothers vaccinated with an mRNA shot during late pregnancy

Any known or possible risks of vaccination for pregnant people are the same as the risks for people who are not pregnant. Also, vaccination does not harm fetuses. 

COVID-19 can cause serious illness and hospitalization in pregnant women. It also can lead to a greater likelihood of pregnancy complications, such as preterm birth or stillbirth.

Speak with your doctor about vaccination if you are pregnant or your immune system is at risk. They can help clear up any questions or concerns.

Consider your personal risks when choosing shots

Speak with your doctor about vaccination if you are pregnant or your immune system is at risk. They can help clear up any questions or concerns.

Public health officials currently favor the two mRNA COVID-19 vaccines (Pfizer and Moderna) over the Johnson & Johnson (Janssen) vaccine for all adult women, including pregnant and lactating women. 

The Johnson & Johnson vaccine carries a rare—but serious—risk of thrombosis with thrombocytopenia syndrome, a blood-clotting condition. Health agencies have confirmed 60 cases among the more than 18.5 million delivered doses. 

Women of reproductive age between ages 30 and 49 are more likely to develop this side effect and should know other options exist, according to the CDC. Symptoms usually show up within six to 14 days after the shot, the American College of Obstetricians and Gynecologists (ACOG) notes.

The Johnson & Johnson vaccine may be appropriate, though, for women who experienced a severe allergic reaction to an earlier mRNA dose.

Moderately or severely immuno-compromised people need additional doses on a shorter timetable to strengthen their protection. This affects people such as:

  • Organ transplant recipients on immune-suppressing medication
  • People with an advanced or untreated HIV infection
  • Patients who are receiving active cancer treatment or taking high-dose corticosteroids or other immune-suppressing medications

The CDC's schedule for immuno-compromised patients recommends a third primary dose of one of the mRNA vaccines at least four weeks after the second primary dose, followed by a booster shot at least three months after the third primary dose. 

Those who received the Johnson & Johnson shot should get a second primary dose at least four weeks after the first primary dose, followed by a booster dose at least two months after the second primary dose.

The CDC suggests an mRNA vaccine for most follow-up doses.

COVID-19 vaccines can cause swelling in your lymph nodes or arm

Women who have been vaccinated against COVID-19 can develop enlarged underarm lymph nodes on the same side where they had the shot. It's more common for this to happen after boosters and additional doses.

The same is true for "COVID arm," a harmless allergic reaction at the site of injection that can cause redness, hardness, itchiness, swelling and pain. 

Localized lymph node swelling is normal for vaccines and doesn't pose any health risks. It can be seen with any vaccine in the arm, says Cedars-Sinai radiologist Dr. Cynthia Litwer

But the enlarged lymph nodes might show up on your mammogram, doctors note.

With so many people getting the vaccine as soon as they are eligible and exhibiting a strong immune response, Dr. Litwer says she has seen this finding in some patients.

While there was initially some concern that this side effect might interfere with mammograms, it has now been determined that mammograms should not be delayed because of an upcoming or recent vaccination. Just be sure to tell the breast technologist doing your exam which arm was injected, the date of the vaccine and which vaccine you received. This information will assist the radiologist in interpreting your mammogram results. 

COVID-19 can cause serious illness and hospitalization in pregnant women. It also can lead to a greater likelihood of pregnancy complications, such as preterm birth or stillbirth.

It might temporarily affect your menstrual cycle

ACOG adds that you might experience a short-lived disruption of your periods after vaccination that could include heavier bleeding, early or late onset of bleeding, or cramping pain.

One study noted minor changes, including variation in cycle length by less than one day, that resolved quickly within two cycles. Providers are monitoring this side effect but emphasize that it appears to be short-lived and doesn't take away from the importance of vaccination.

"Despite minor changes in cycle length, at this point fertility potential does not appear to be affected by vaccination," said Dr. Margareta Pisarska, director of the Division of Reproductive Endocrinology and Infertility at Cedars-Sinai

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Margareta D. Pisarska, MD

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