CDC Study in Kenya Suggests Being Pregnant Doubles the Risk of Flu Illness

February 4, 2022 — new study by CDC authors and global partners in the journal Influenza and Other Respiratory Viruses highlights the burden of flu among pregnant woman and their infants in the tropical African nation of Kenya as part of a broader effort to raise flu vaccination rates among pregnant women globally. The study found that women were twice as likely to get sick with flu during their pregnancy compared to after their pregnancy and that flu illness also was more common among women with HIV. Like many middle-income countries, Kenya does not have a flu vaccination program. This study, which underscores potential benefits from maternal flu vaccination in Kenya, is the latest study in an international effort to document the global burden of flu among pregnant women to help inform policy for the use of maternal influenza vaccination.

In the U.S. pregnant women have been known to be at higher risk of developing serious flu complications for many years. In 1960, the US Surgeon General first recommended influenza vaccination for people at high risk, including pregnant women. About 61% of pregnant women in the U.S. get an annual flu vaccine. Internationally, flu vaccination programs are rare, particularly among lower and middle-income countries. CDC’s international flu program has been working since 2014 to establish an evidence base to inform flu vaccine policy in other countries. This effort has resulted in 12 studies looking at the burden of flu and potential benefit of vaccination among pregnant women in list countries.

This study in Kenya is among few that have explored flu disease burden among pregnant women in tropical or middle-income countries. The study in Kenya enrolled 3,026 pregnant women and 2,550 infants during June 2015 through May 2020. The study looked for prenatal incidence of laboratory-confirmed flu among mothers and postnatal incidence among mothers and infants. The study confirmed that pregnant women were more likely to get sick from flu during their pregnancy compared with after they give birth. Additionally, like Kenya, many tropical areas of Africa have higher prevalence of diseases like HIV, tuberculosis (TB), and malaria that may influence both the incidence and complications of flu illness.

The World Health Organization (WHO) recommended in 2012 that countries prioritize pregnant women for flu vaccination. This study’s findings suggests that Kenyan authorities should consider the value of vaccinating pregnant women, especially if they are HIV-infected because they are at higher risk for severe influenza illness or mortality.

This eight-year program was supported by funding from the U.S. Centers for Disease Control and Prevention through the National Center for Immunization and Respiratory Diseases (NCIRD), Influenza Division. Partners in this endeavor included Australia, Canada, China, El Salvador, India, Israel, Kenya, Laos, Panama, Peru, South Africa, Thailand, and the United States.

Previous U.S studies have shown that pregnant women are at higher risk for flu-related complications and hospitalization and frequently seek medical care for flu-related illness. Changes to the immune system, heart, and lungs during pregnancy make people more susceptible to influenza severe enough to cause hospitalization throughout pregnancy and up to two weeks postpartum. Influenza also may be harmful for the developing baby. Influenza illness may be associated with late pregnancy loss or low birth weight. Parental vaccination also can help protect a baby from influenza after birth (because antibodies are passed to a developing baby during pregnancy).

Getting an influenza (flu) vaccine is the first and most important step in protecting against flu. Pregnant people should get a flu shot. Flu shots given during pregnancy help protect both the pregnant parent and the baby from flu. A list of recent studies on the benefits of flu vaccination for pregnant people is available.

For more information about flu vaccination during pregnancy visit: Flu & Pregnancy | CDC. More information about flu vaccine safety during pregnancy is available at Flu Vaccine Safety and Pregnancy.

You can find this study and similar one available online:

  1. Cost-effectiveness of seasonal influenza vaccination in pregnant women, healthcare workers and adults >= 60 years of age in Lao People’s Democratic Republic – PubMed (
  2. The burden of influenza among Kenyan pregnant and postpartum women and their infants, 2015–2020 – Otieno – – Influenza and Other Respiratory Viruses – Wiley Online Library
  3. Incidence rates of influenza illness during pregnancy in Suzhou, China, 2015–2018 – Chen – – Influenza and Other Respiratory Viruses – Wiley Online Library
  4. Incidence of influenza and other respiratory viruses among pregnant women; a multi-country, multiyear cohort – PubMed (
  5. Realizing the Potential of Maternal Influenza Vaccination – PubMed (
  6. Full article: What do pregnant women think about influenza disease and vaccination practices in selected countries (
  7. Incidence of influenza during pregnancy and association with pregnancy and perinatal outcomes in three middle-income countries: a multisite prospective longitudinal cohort study – The Lancet Infectious Diseases
  8. Respiratory Viral Infections and Infection Prevention Practices Among Women With Acute Respiratory Illness During Delivery Hospitalizations During the 2019–2020 Influenza Season | The Journal of Infectious Diseases | Oxford Academic (
  9. An international cohort study of birth outcomes associated with hospitalized acute respiratory infection during pregnancy – ScienceDirect
  10. A cost-effectiveness analysis of antenatal influenza vaccination among HIV-infected and HIV-uninfected pregnant women in South Africa – ScienceDirect
  11. Influenza Vaccine Effectiveness in Preventing Influenza-associated Hospitalizations During Pregnancy: A Multi-country Retrospective Test Negative Design Study, 2010-2016 – PubMed (
  12. Safety, tolerability, and immunogenicity of a single dose 4-antigen or 3-antigen Staphylococcus aureus vaccine in healthy older adults: Results of a randomised trial – PubMed (