The first concern for mothers during flu season is the impact of the flu virus on pregnancy.
Previous influenza pandemic data (including pandemics in 1918~1919, 1957~1958, and 2009~2010) show that pregnant women have a more severe clinical course and a higher risk of hospitalization, ICU admission, and death than the general population. In addition, during the 2009–2010 pandemic season, 12% of pregnancy-related deaths were attributed to confirmed or suspected H1N1 influenza.
At the same time, infection with influenza viruses during pregnancy may be related to congenital anomalies in the fetus. A 2013 meta-analysis of observational studies showed that influenza or influenza-like illness in early pregnancy was associated with an increased risk of congenital anomalies (AOR 2, 95% CI 1.62 to 2.48), including cleft lip (OR 3.2), neural tube defects (OR 3.3), hydrocephalus (OR 5.7), and congenital heart defects (OR 1.6).
Since influenza is extremely harmful to mothers and fetuses, can oral anti-disease drugs be taken in advance to prevent the disease before it happens?
1. Do I need oral antiviral drugs for prophylaxis?
Can I be prevented with oral antivirals if I have not been exposed to a person with influenza (before exposure)?
A: Pre-exposure antiviral drugs are not routinely recommended.
However, pregnant women who have contraindications to influenza vaccination, do not have access to influenza vaccine, or are expected to be ineffective with influenza vaccination (e.g., due to immunosuppression or mismatch of vaccine antigens with epidemic strains). As soon as influenza activity in the community is detected, pre-exposure prophylaxis should be initiated immediately.
Can I be prevented with oral antivirals after exposure to people who have been exposed to influenza?
Answer: Post-exposure antiviral prophylaxis is not routinely recommended.
However, oral antiviral prophylaxis may be considered in pregnant women who are asymptomatic within 48 hours of exposure and have the following two conditions:
1. Influenza vaccine is not available or is expected to be ineffective after influenza vaccination (e.g., due to immunosuppression or mismatch of vaccine antigens with the circulating strain) and home influenza exposure has occurred.
2. Are a household contact of a group at high risk of influenza complications, have not been vaccinated, and have had influenza exposure.
What are the specific protocols for oral antivirals to prevent influenza?
Answer: Recommended Preventive Dosage and Duration:
1. Oseltamivir, 75 mg each time, once a day, for 7 days;
2. Zanamivir, 10 mg each time (5 mg per inhalation, a total of 2 inhalations), once a day, for 7 days.
Note: A reasonable alternative to the above pre- and post-exposure prophylaxis is early initiation of therapy in patients with symptomatic disease.
Is wearing a mask still useful during flu season?
Answer: It is recommended.
After the new crown, everyone began a new round of questions about the prevention and treatment of masks, is wearing masks effective in preventing viral respiratory infections?
Neither the mainland influenza vaccine guidelines nor the expert consensus on maternal influenza prevention and control specifically mention the role and effectiveness of masks in preventing "influenza". However, from the literature review analysis, wearing masks still has a certain protective effect on preventing respiratory viral infections.
A 2022 systematic review analysing the role of different types of masks in respiratory viral infections showed that mask wearing (high adherence) provided significant protection (OR 0.43; 95% CI, 0.23-0.82), and N95 may be more effective.
Source: References
2. Treatment of influenza during pregnancy
Does a negative test result for influenza virus in pregnancy exclude a flu diagnosis?
A: A negative influenza virus test result does not exclude infection, especially if the test used is not sensitive enough or a false-negative result may occur when a sample is collected 4 days > the onset of illness. Epidemiological exposure and symptoms are therefore critical.
The following is a comparison of the clinical features of influenza and the common cold.
Table 1: Influenza and the common cold
Suspected influenza diagnosis during pregnancy, antibody results are not available, can antiviral therapy be available?
Answer: Suspected diagnosis, early medication recommended (within 48 hours)
The mainland's 2019 "Expert Consensus on the Prevention and Treatment of Maternal Influenza" clearly pointed out that during the influenza season, pregnant women with influenza-like symptoms should start anti-influenza virus treatment as soon as possible after excluding other causes, without waiting for virus test results.
Early treatment (no more than 48 hours after symptom onset) reduces the risk of ICU admission or death. However, critically ill patients with onset longer than 48 hours may still benefit from antiviral therapy.
What are the specific treatment options for anti-influenza virus during pregnancy?
Answer: Anti-influenza virus treatment regimens during pregnancy are the same as for non-pregnant adults:
Preferred: oseltamivir 75 mg twice daily for 5 days
Alternatives: zanamivir 10 mg twice daily for 5 days, or peramivir as a single dose of 600 mg intravenously (instillation time at least 15 minutes)
Note: The usual course of oseltamivir is 5 days; However, an extended course (up to 10 days) may be required in immunocompromised or severely ill patients, particularly those whose influenza virus RNA is detectable on respiratory specimens after 5 days of antiviral therapy.
3. Influenza vaccination during pregnancy
Continental guidelines explicitly recommend influenza vaccination for all pregnant women (regardless of stage of pregnancy), potential pregnant, or postpartum patients during influenza season.
Which flu vaccine should I choose during pregnancy? How to get vaccinated?
A: 1 dose of trivalent and quadrivalent inactivated influenza vaccines is recommended for pregnant women.
Pregnant women can receive any approved inactivated influenza vaccine or recombinant influenza vaccine. Live attenuated vaccine should not be given. Continental influenza vaccination guidelines clearly state that children and adults aged 9 years ≥ only need 1 dose.
Table 2.Types of continental influenza vaccines and applicable populations Made based on Reference 7
4. Safety of influenza vaccine and antiviral drugs during pregnancy
Do anti-influenza virus drugs increase the risk of fetal malformations?
A: There is currently no clear evidence that anti-influenza virus drugs increase the occurrence of fetal malformations.
Oseltamivir, zanamivir, and peramivir are classified as Class C drugs in pregnancy by the US Food and Drug Administration (FDA) (with caution). No serious adverse effects have been found in pregnant women and fetuses, and the benefits of treatment (at the beginning) far outweigh the potential maternal-fetal harms.
A 2019 US prospective study of 716 pregnant women showed that patients taking oseltamivir (n = 112) had similar rates of major birth anomalies, preterm birth, and small-for-gestational-age infants compared with those who did not.
In another retrospective study, also from the US, including more than 12,500 infants, infants exposed to oseltamivir (n = 121) had similar rates of congenital anomalies compared with those without this exposure, with the exception of malrotation (13 versus 3.5%, OR 10.7, 95% CI 1.8 to 45.2). Intestinal dysrotation was found in 3 patients exposed to oseltamivir, but further research is needed to determine whether there is a clear causal relationship with drug use.
Can flu vaccination during pregnancy cause fetal malformations?
Answer: Influenza vaccination during pregnancy does not increase the risk of fetal malformations.
The mainland's 2019 "Expert Consensus on the Prevention and Treatment of Maternal Influenza" clearly pointed out that influenza vaccination during pregnancy does not increase the risk of fetal malformations. Previous severe allergic reaction to influenza vaccine is the only contraindication to influenza vaccination.
In fact, influenza vaccination during pregnancy not only protects mothers, but also reduces the risk of influenza infection in the first months of life.
Prenatal maternal immunity induces the production of large amounts of anti-influenza-specific serum IgG, which can be passed through the placenta to the fetus; During lactation, anti-influenza-specific IgA can be passed to infants through breast milk. Infants under 6 months of age are not eligible for influenza vaccination, and maternal vaccination is the only way to gain immunity.
Scientific review: Deputy Chief Physician of Department of Obstetrics and Gynecology, Second People's Hospital of Guangdong Province
Bibliography:
1. Perinatal Medicine Branch of Chinese Medical Association, Editorial Board of Chinese Journal of Perinatal Medicine. Expert consensus on maternal influenza prevention and control[J]. Chinese Journal of Perinatal Medicine,2019,22(2):73-78.
2、Luteijn JM, Brown MJ, Dolk H. Influenza and congenital anomalies: a systematic review and meta-analysis. Hum Reprod 2014; 29:809.
3、Chambers CD, Johnson D, Xu R, et al. Oseltamivir use in pregnancy: Risk of birth defects, preterm delivery, and small for gestational age infants. Birth Defects Res 2019; 111:1487.
4、Van Bennekom CM, Kerr SM, Mitchell AA. Oseltamivir exposure in pregnancy and the risk of specific birth defects. Birth Defects Res 2019; 111:1479.
5. Uptodate, seasonal flu and pregnancy
6. Uptodate, the treatment of seasonal influenza in non-pregnant adults
7. Influenza Vaccine Working Group of the Technical Working Group of National Immunization Program. Technical guidelines for influenza vaccine vaccination in China (2022—2023)[J] . Chinese Journal of Preventive Medicine, 2022, 56(10) : 1356-1386.