The US Centers for Disease Control reported this week that the peak of the flu season has finally passed, and new cases of flu are starting to decline. But it’s not over yet. Many more cases of flu are expected to be reported. This means that if you have not received a flu vaccine this season, you should still get one.
I am asked all the time about vaccinations in pregnancy. Which vaccines are safe in pregnancy? What if I received a vaccination before I realized that I was pregnant? Can I get sick from a vaccination? To answer these questions, let’s talk about how vaccines work, then you’ll see why we recommend a few of them in pregnancy.
What vaccines are and how they actually work
A vaccine is like a stunt double for a germ. In other words, your body thinks the vaccine is a bacteria or virus, but it’s an imitation, made by killing or weakening the germ. When your body encounters that vaccine, it makes antibodies against the disease. This way, if you are exposed to the actual germ, you are protected.
There are a couple of reasons that we want you to be immune to preventable infections in pregnancy. For one thing, pregnant women tend to get sicker than their non-pregnant counterparts when they get infections like flu, measles, and chicken pox. So ideally, you should be up to date on all routine vaccinations (tetanus, measles, rubella, mumps, polio, hepatitis B) before getting pregnant.
Secondly, we want to protect your baby until they receive their first vaccinations.
Vaccinating pregnant moms protects babies by allowing them to pass antibodies to baby, so that when the baby is born, he or she already carries some antibodies to certain diseases. There is also a phenomenon called “herd immunity” or “cocooning.” This means that when everyone around the baby is vaccinated against a disease, the baby is much less likely to get exposed to the disease.
Two vaccinations that are routinely recommended in pregnancy
There are two commonly recommended vaccines during pregnancy. Let’s dive into what they are and how they work to protect you and your baby.
This vaccine protects against tetanus, diphtheria, and pertussis (whooping cough).
Pertussis is a respiratory infection, and is actually on the rise in the US, because most of us were vaccinated in childhood, and our immunity decreases over time. Babies who develop pertussis usually catch it from their mothers.
The Tdap vaccine gives you immunity, so you won’t get pertussis and pass it to your baby. And when you receive the Tdap between weeks 27 and 36 of pregnancy, you give some of your antibodies to the fetus, so the baby is born with some built-in protection. It takes a few weeks for you to make antibodies and share them with the fetus, hence the timing of the vaccine. We recommend that you get a new Tdap with every pregnancy, even if you get pregnant again within a year.
Why? Because your level of antibody declines, so the new baby won’t be born with enough antibodies to fight off pertussis if you don’t get a new vaccine.
The flu vaccine is made brand new every year, because the flu virus mutates rapidly, and new strains appear each year.
Laboratories try to predict which strains of influenza will be most prevalent each year, and they make the flu vaccine to protect you from these particular strains. The flu shot is made from killed or recombinant (fake) flu virus, so it can’t give you the flu. A vaccination may cause redness at the injection site, or low grade fever or muscle aches briefly, but this is not the flu. Any symptoms are simply the result of your body getting busy making antibodies.
If you didn’t receive a flu vaccine this season, I am giving you the stink-eye right now.
A few more vaccines you may encounter during pregnancy
There are other vaccines that are sometimes given to pregnant women if they have a risk for a particular infection.
The tetanus vaccine is a toxoid vaccine, meaning that it’s made from the inactivated toxin produced by tetanus. It is safe in pregnancy. If you have a minor injury like a cut or puncture wound and you haven’t received a tetanus shot in the last 5 years, you need one. If you don’t have an injury, your last tetanus shot is good for 10 years. The Tdap contains tetanus vaccine, so it counts as your 10-year tetanus booster.
If you will be traveling to an area where there is a lot of hepatitis B, or are at high risk for developing hepatitis B (because of behaviors like drug use or sexual contact), we recommend that you be vaccinated, preferably before getting pregnant. The hepatitis B vaccine is made from recombinant (fake) virus, so it’s safe in pregnancy if you need to receive it. It is given in 3 installments a few months apart. If you are in the middle of the series when you become pregnant, it’s okay to complete the series.
As with hepatitis B, if you are traveling to an area with yellow fever (and let me just say: don’t), you should be vaccinated prior to travel. The yellow fever vaccine is a live weakened virus, and live virus vaccines carry a risk of infecting the fetus. So don’t get a yellow fever vaccine in pregnancy unless you are at high risk for becoming infected with yellow fever.
If you have not been vaccinated against polio and will be traveling to an area where you may be exposed, you should get the polio vaccine. Like the yellow fever vaccine, polio vaccine is made from live virus, so don’t get the vaccine unless you know you are at high risk for exposure to polio.
Every now and then, someone receives a live vaccine (rubella, chicken pox, measles, mumps, polio, yellow fever) in early pregnancy, or becomes pregnant within a month after a vaccination. Although it’s not ideal to receive a live vaccine in pregnancy, there are NO reported cases of harm to fetuses as a result of a live vaccine. So while we don’t recommend that you get live vaccines during or just prior to pregnancy, they are not considered deal-breakers. We usually test for immunity to rubella (German measles) in pregnancy because rubella in pregnancy can cause major birth defects in fetuses.
We vaccinate you after delivery if you are non-immune, so that you won’t get rubella.
The last word: Get any needed vaccines prior to pregnancy when possible, ask your OB provider before receiving any vaccines, and tell your OB if you plan to travel or are exposed to any infectious diseases during pregnancy. And get your flu shot and Tdap!