A new study shows that receiving the flu vaccine during pregnancy, particularly during the second and third trimesters, was associated with a significantly lower risk of flu infection in the newborn child. This is another reason to get the proper vaccines during pregnancy to protect the newborn baby.

This study adds to the list of vaccines that expectant mothers should receive to protect their newborns. These vaccines include the RSV vaccine for respiratory syncytial virus, Tdap for tetanus, diphtheria, and whooping cough (pertussis), and the COVID-19 vaccine for COVID.

This article will examine new research that claims that the flu vaccine during pregnancy reduces the risk of flu infection in newborns.

Flu vaccine and pregnancy study

In a paper published on 26 June 2025 in Obstetrics and Gynecology, Ousseny Zerbo, PhD, Kaiser Permanente Northern California (KPNC), Oakland, CA, and colleagues, utilized a study cohort that consisted of pregnant individuals enrolled in KPNC from 2011 to 2022 and their 245,498 infants, who were followed from birth until the first occurrence of a positive polymerase chain reaction test result for influenza, the infant reached 6 months of age, death, disenrollment from KPNC, or the end of the study period.

Below is the reduction in flu risk among newborns after the mother received the flu vaccine:

• First trimester vaccination — 11.3%
• Second trimester — 51.5%
• Third trimester — 59.3%

The risk reduction was only statistically significant for second- and third-trimester vaccinations.

Additionally, this new study found the following after maternal vaccination against the flu:

• 51.4% reduction in flu infection for infants 0 to 60 days
• 55.5% reduction for infants 61 to 120 days
• 28.5% reduction for infants 121 to 180 days.

This research adds more data to the effectiveness of the flu vaccine during pregnancy. For example, the flu can cause a more severe disease in pregnant women. Another study showed that flu vaccination during pregnancy, especially in the second half, reduces the risk of influenza infection in infants by 30-63% during their first 6 months

Infants under six months old are not eligible to receive the flu vaccine, so the only way to protect them is through the mother. Unfortunately, there are more serious complications for babies who contract the flu.

Typically, flu disease lasts in children 3-7 days, but it may take longer for the baby to recover. Also, some babies may develop severe complications such as pneumonia, seizures, or brain inflammation. In those cases, hospitalization and recovery may take much longer. So far in the 2024-25 flu season, 253 babies have died from the flu.

Summary

The evidence is overwhelming — getting the flu vaccine during pregnancy protects the baby against this dangerous disease. It can save their lives.

Unfortunately, flu vaccine uptake among pregnant women is low, at around 47.4%. I hope studies like the one discussed in this article will increase that so that we can protect babies.

If you are pregnant, get the flu vaccine. It’s safe. And it’s effective in preventing serious disease during pregnancy and protecting your newborn baby.

Citations

• Getahun D, Liu IA, Sy LS, Glanz JM, Zerbo O, Vazquez-Benitez G, Nelson JC, Williams JT, Hambidge SJ, McLean HQ, Irving SA, Weintraub ES, Qian L. Safety of the Seasonal Influenza Vaccine in 2 Successive Pregnancies. JAMA Netw Open. 2024 Sep 3;7(9):e2434857. doi: 10.1001/jamanetworkopen.2024.34857. PMID: 39298167; PMCID: PMC11413712.
• Omer SB, Clark DR, Madhi SA, Tapia MD, Nunes MC, Cutland CL, Simões EAF, Aqil AR, Katz J, Tielsch JM, Steinhoff MC, Wairagkar N; BMGF Supported Maternal Influenza Immunization Trials Investigators Group. Efficacy, duration of protection, birth outcomes, and infant growth associated with influenza vaccination in pregnancy: a pooled analysis of three randomised controlled trials. Lancet Respir Med. 2020 Jun;8(6):597-608. doi: 10.1016/S2213-2600(19)30479-5. PMID: 32526188; PMCID: PMC7284303.
• Zerbo O, Modaressi S, Goddard K, Fireman B, Klein NP. Influenza Vaccination During Pregnancy and Infant Influenza in the First 6 Months of Life. Obstet Gynecol. 2025 Jun 26. doi: 10.1097/AOG.0000000000005986. Epub ahead of print. PMID: 40570349.

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