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Seasonal influenza and pregnancy

Seasonal influenza and pregnancy
Literature review current through: Jan 2024.
This topic last updated: Dec 08, 2023.

INTRODUCTION — Influenza is an acute respiratory illness caused by influenza A or B viruses that occurs in outbreaks and epidemics worldwide, mainly during the winter season [1-4]. Influenza-associated morbidity and mortality are higher among pregnant and recently postpartum patients (within two weeks after delivery or pregnancy loss) than the general population [3].

This topic will discuss issues specific to seasonal influenza in pregnant and postpartum patients. Information on seasonal influenza in nonpregnant patients is discussed separately:

(See "Influenza: Epidemiology and pathogenesis".)

(See "Seasonal influenza in adults: Clinical manifestations and diagnosis".)

(See "Seasonal influenza in nonpregnant adults: Treatment".)

(See "Seasonal influenza in adults: Role of antiviral prophylaxis for prevention".)

(See "Antiviral drugs for influenza: Pharmacology and resistance".)

(See "Seasonal influenza vaccination in adults".)

CLINICAL MANIFESTATIONS — Clinical manifestations of influenza in pregnant and postpartum patients are similar to those in the general population, but the symptoms are typically more severe. Influenza characteristically begins with the abrupt onset of fever, nonproductive cough, and myalgia. Fever usually ranges from 37.8 to 40.0°C (100 to 104°F). Other nonspecific symptoms include malaise, sore throat, nausea, nasal congestion, and headache. (See "Seasonal influenza in adults: Clinical manifestations and diagnosis".)

These clinical features overlap substantially with those of other respiratory viral illnesses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; the virus that causes coronavirus disease 2019 [COVID-19]), and there is no way to accurately distinguish between them in the absence of diagnostic testing. In addition, coinfection with influenza and SARS-CoV-2 can occur, albeit rarely. (See "Seasonal influenza in adults: Clinical manifestations and diagnosis", section on 'Differential diagnosis'.)

EFFECTS ON PREGNANCY

Maternal effects — Data from influenza pandemics over the last century (including the pandemics of 1918 to 1919, 1957 to 1958, and 2009 to 2010) have shown that pregnant patients are more likely to have a more severe clinical course, be hospitalized and admitted to an intensive care unit, and to die compared with the general population [3,5-13]. Pregnant patients with comorbidities (eg, chronic cardiac or pulmonary disease, diabetes mellitus, chronic renal disease, malignancy, immunosuppression) are at an even greater risk of complications from influenza than their nonpregnant counterparts [8].

During the 2009 H1N1 pandemic, pregnant individuals accounted for 5 percent of all influenza deaths even though they comprised only 1 percent of the United States population [14,15]. In addition, 12 percent of pregnancy-related deaths during the 2009 to 2010 pandemic season were attributed to confirmed or suspected H1N1 influenza A virus infection [16].

In a subsequent retrospective study including more than 2600 pregnant patients hospitalized with influenza between 2010 and 2019 (most of whom were in their third trimester and only one-third of all patients were vaccinated against influenza), severe maternal illness requiring intensive care occurred in 5 percent [17]. There were eight maternal deaths (half of which occurred in the unvaccinated group). Influenza A H1N1, when compared with other influenza subtypes, was associated with more severe maternal outcomes.

Fetal effects — Transplacental transmission of influenza virus appears to be rare [18]. However, maternal influenza during pregnancy may have adverse effects on the fetus even in the absence of transplacental transmission.

Maternal influenza virus infection may be associated with fetal congenital anomalies. In a systematic review and meta-analysis of observational studies, influenza or influenza-like illness in the first trimester was associated with an increased risk of congenital abnormalities (adjusted odds ratio [OR] for any anomaly 2, 95% CI 1.62-2.48), including cleft lip (OR 3.2), neural tube defects (OR 3.3), hydrocephaly (OR 5.7), and congenital heart defects (OR 1.6) [19]. Hyperthermia, a common clinical manifestation of influenza, is also a risk factor for certain congenital anomalies; this risk appears to be attenuated by use of antipyretics [20]. (See 'Symptom management' below and "Neural tube defects: Overview of prenatal screening, evaluation, and pregnancy management", section on 'Fever/hyperthermia'.)

Maternal influenza during pregnancy may also be associated with an increased risk for pregnancy loss, preterm birth, low birth weight, birth of a small-for-gestational-age (SGA) infant, and fetal death [5,11,21-28]. In the 2009 H1N1 pandemic, only severely ill pregnant patients (ie, those admitted to an intensive care unit) had a substantially increased risk of poor infant outcomes (eg, preterm labor, low birth weight) [29]. In the retrospective study including pregnant patients hospitalized with influenza and mentioned above (see 'Maternal effects' above), fetal loss occurred in 3 percent of patients no longer pregnant at discharge; the majority of these losses occurred in the first and second trimesters [17].

DIAGNOSIS — The diagnosis of influenza should be suspected in patients with abrupt onset of fever, cough, and myalgia when influenza virus activity is present in the community (in the northern hemisphere, typically September to April; in the southern hemisphere, typically April to September). Other symptoms, such as malaise, sore throat, nausea, nasal congestion, and headache, are common in the setting of influenza as well.

A positive test for influenza virus confirms the diagnosis. However, a negative test for influenza virus cannot rule out infection, especially if the test does not have adequate sensitivity or if the specimen was collected >4 days after illness onset. (See "Seasonal influenza in adults: Clinical manifestations and diagnosis", section on 'Diagnosis of influenza'.)

Pregnant and recently postpartum patients (within two weeks after delivery) with suspected influenza should also undergo testing for SARS-CoV-2. (See "COVID-19: Diagnosis".)

MANAGEMENT

Infection control measures — General issues related to infection control measures for prevention of seasonal influenza (eg, hand and respiratory hygiene, droplet precautions) are the same as for nonpregnant patients and are presented in the table (table 1) and discussed in detail separately. (See "Infection control measures for prevention of seasonal influenza".)

Pregnant and recently postpartum patients — Pregnant and recently postpartum patients (within two weeks after delivery) at moderate to increased risk for complications include those with [4]:

Inability to retain fluids

Signs of dehydration

Shortness of breath

Chest pain or pressure

Altered mental status

Comorbidities (eg, human immunodeficiency virus [HIV], asthma)

Obstetric complications (eg, preterm labor)

Worsening symptoms after previous improvement

Inability to care for self

These patients should be referred immediately to an emergency department or equivalent setting for evaluation, possible admission, and treatment. Hospitalization is warranted for patients with significant dehydration and for severely ill patients, especially those with respiratory distress, hypoxemia, impaired cardiopulmonary function, or altered mental status. For patients at risk for complications but without these findings, admission for observation may be warranted.

Patients without an increased risk of complication may be managed via phone or other remote communication unless other issues warrant an office visit. In such cases, plans should be made for follow-up by phone in 24 to 48 hours to assess change in status.

Antiviral treatment — Decisions regarding antiviral treatment for influenza should be based on clinical circumstances and current information regarding circulating influenza virus in the community; antiviral treatment should not be withheld while awaiting results of diagnostic testing (including testing for SARS-CoV-2 [ie, COVID-19]). (See 'Diagnosis' above.)

Timing — For pregnant and postpartum patients (within two weeks of delivery) with suspected or confirmed influenza, we recommend antiviral treatment as early as possible, regardless of vaccination status. While the benefits of antiviral therapy are greatest when initiated within the first 48 hours following symptom onset, antiviral treatment is also warranted for patients who present >48 hours after symptom onset, particularly if their clinical condition has not started to improve.

Delay of treatment is associated with worse outcomes. In one retrospective study including 788 pregnant patients with 2009 H1N1 influenza, those who received treatment >4 days compared with ≤2 days after symptom onset were more likely to be admitted to an intensive care unit (56.9 versus 9.4 percent; relative risk [RR] 6; 95% CI 3.5-10.6) [14]. Similarly, in a subsequent retrospective study including 959 pregnant patients with 2009 H1N1 influenza, those who received antiviral treatment ≥2 days compared with <2 days after diagnosis were more likely to be hospitalized (OR 3.4, 95% CI 1.6-7.6) [30].

Antiviral agents — Information regarding antiviral selection, dosing, and duration for pregnant patients is outlined below. Additional information related to antiviral agents is discussed in detail separately. (See "Seasonal influenza in nonpregnant adults: Treatment", section on 'Antiviral agents'.)

SelectionOseltamivir is the preferred antiviral agent for treatment of pregnant patients with influenza as it is the agent for which there is greatest clinical experience [31]. Other neuraminidase inhibitors (ie, zanamivir, peramivir) are acceptable alternative agents for treatment of pregnant patients; however, zanamivir is relatively contraindicated in patients with asthma or chronic obstructive pulmonary disease and peramivir is only available intravenously.

Baloxavir is not generally recommended for pregnant or postpartum patients given lack of safety and efficacy data. If there is a compelling reason to use baloxavir during pregnancy, the risks and benefits must be weighted carefully [31].

Dosing – Dosing of antiviral agents for treatment of influenza during pregnancy is the same as in nonpregnant adults [4,31]:

Preferred agent:

-Oseltamivir 75 mg twice daily for five days (preferred)

Alternative agents:

-Zanamivir 10 mg (two 5 mg inhalations) twice daily for five days or

-Peramivir 600 mg intravenously (infused over a minimum of 15 minutes) administered as a single dose

There is no role for increasing the oseltamivir dose, given the lack of greater benefit at higher doses [32].

Duration – In general, we administer oseltamivir for five days.

A longer duration of treatment (up to 10 days) may be warranted for immunocompromised or severely ill patients, particularly in those who continue to have detectable influenza virus ribonucleic acid (RNA) from a respiratory specimen after five days of antiviral treatment. (See "Seasonal influenza in nonpregnant adults: Treatment", section on 'Antiviral duration'.)

Safety data

Pregnancy – Data on the safety of oseltamivir, zanamivir, and peramivir during pregnancy are limited, especially during the first trimester; however, the benefits of early treatment appear to outweigh the potential risks [31].

In a meta-analysis including nine cohort studies evaluating neonatal outcomes after exposure to neuraminidase inhibitors during pregnancy, those exposed to neuraminidase inhibitors compared with unexposed infants had similar rates of preterm birth, congenital malformations, and low Apgar scores [33]. In addition, exposure to neuraminidase inhibitors was associated with reduced rates of low birth weight (odds ratio [OR] 0.79, 95% CI 0.68-0.92) and small-for-gestational-age (SGA) infants (OR 0.78, 95% CI 0.69-0.88). In one retrospective study not included in this meta-analysis, rates of intestinal malrotation were increased among infants exposed to oseltamivir (3 out of 121 infants; OR 10.7, 95% CI 1.8-45.2) [34]. However, given this association is based only on three infants, and the OR had wide confidence intervals, the authors noted that this finding might be due to chance. This association has not been described previously and requires further study.

Lactation – Use of oseltamivir by breastfeeding mothers appears to pose no harm to their infants [35,36]. The drug and its active metabolite are poorly excreted into breast milk [37].

We are not aware of any studies on the safety of zanamivir or peramivir during breastfeeding.

Symptom management — Acetaminophen is used to treat fever [38], since hyperthermia during the first trimester has been associated with neural tube defects and possibly other congenital anomalies (see 'Fetal effects' above). In addition, fever during labor may be a risk factor for neonatal seizures, encephalopathy, cerebral palsy, and neonatal death [20,39,40]. (See "Prenatal care: Patient education, health promotion, and safety of commonly used drugs", section on 'Acetaminophen'.)

Other antipyretics (eg, aspirin, nonsteroidal antiinflammatory drugs [NSAIDs]) should be avoided as they may be associated with adverse pregnancy and infant outcomes (eg, oligohydramnios, premature closure of the ductus arteriosus); low-dose aspirin given for obstetric indications may be continued during pregnancy. (See "Prenatal care: Patient education, health promotion, and safety of commonly used drugs", section on 'NSAIDs'.)

Symptomatic therapy (for cough, rhinorrhea, sore throat, headache, and myalgia) is similar to that for pregnant patients with the common cold and is reviewed separately. (See "Approach to the pregnant patient with a respiratory infection", section on 'The common cold'.)

Concomitant infection — Empiric treatment for concomitant bacterial pneumonia (in addition to antiviral treatment for influenza) is warranted for selected patients with influenza including patients who [3]:

Present with respiratory failure and/or hemodynamic instability, or

Fail to improve after three to five days of antiviral therapy and supportive care, or

Develop fever after defervescence

Antibiotic selection should be guided by Gram stain and culture of sputum, if available. If the etiology of the pneumonia is uncertain, empiric antibiotics effective against the organisms commonly implicated in secondary bacterial pneumonia among patients with influenza (Streptococcus pneumoniae, Streptococcus pyogenes, and Staphylococcus aureus) should be used.

Agents with activity against S. pneumoniae and S. pyogenes include third-generation cephalosporins (such as ceftriaxone). Empiric treatment for methicillin-resistant S. aureus infection with vancomycin should be initiated in patients with severe or necrotizing pneumonia [3]. (See "Treatment of community-acquired pneumonia in adults who require hospitalization".)

Role of fetal monitoring — There are no published guidelines for fetal monitoring during or after maternal influenza virus infection. The type and frequency of fetal surveillance is determined on a case-by-case basis and guided by the patient's overall condition and the health care provider's judgment. Decisions about timing of delivery should be based on standard obstetric indications. (See "Overview of antepartum fetal assessment", section on 'Indications for fetal assessment'.)

Newborns

Routine care – Asymptomatic newborns (born in the hospital with infection control precautions) should be considered exposed, not infected; these newborns may receive care in the nursery using standard precautions and should be observed for signs of infection.

Issues related to clinical manifestations, diagnosis, and management of children with influenza are discussed separately. (See "Seasonal influenza in children: Clinical features and diagnosis" and "Seasonal influenza in children: Management".)

Considerations for temporary separation – Given the risk of influenza complications in newborns, the United States Centers for Disease Control (CDC) recommends considering temporary separation of a mother with suspected or confirmed influenza from the newborn (with feedings of expressed breast milk or formula provided by a healthy caregiver). The duration of separation is individualized; there are no data on which to formulate evidence-based recommendations. CDC guidelines developed during the 2009 H1N1 pandemic recommended separation until all of the following criteria were met [41]:

The mother has received antiviral medication for 48 hours.

The mother has been afebrile without antipyretics for >24 hours.

The mother can control coughing and respiratory secretions.

If temporary separation is not feasible, physical distancing (eg keeping the healthy newborn >6 feet away from the ill mother as feasible) is advisable.

Role of antiviral prophylaxis – For asymptomatic healthy-term newborns, routine use of oseltamivir for prophylaxis is not recommended given limited safety and efficacy data in this age group.

Issues related to influenza prophylaxis in children are discussed in detail separately. (See "Seasonal influenza in children: Prevention with antiviral drugs".)

Household contacts and infant caregivers — Issues related to antiviral prophylaxis for household members and infant caretakers who have close contact with an individual with influenza are discussed separately. (See "Seasonal influenza in adults: Role of antiviral prophylaxis for prevention", section on 'Postexposure antiviral prophylaxis'.)

All eligible household members (including children ≥6 months of age) and infant caretakers should be vaccinated against influenza virus. (See 'Prevention' below and "Seasonal influenza vaccination in adults" and "Seasonal influenza in children: Prevention with vaccines".)

PREVENTION

Vaccination — We recommend influenza virus vaccination for all patients who are pregnant or might be pregnant or postpartum (within two weeks after delivery) during influenza season; this is consistent with the recommendations from the United States Centers for Disease Control (CDC) Advisory Committee on Immunization Practices (ACIP) and American College of Obstetricians and Gynecologists (ACOG) [1,42].

Administration

Timing – For pregnant patients in the first or second trimester during the summer months, influenza vaccination should be offered before community onset of influenza virus activity (during September or October in the northern hemisphere and during March or April in the southern hemisphere) [1].

For pregnant patients in the third trimester during the summer months, earlier vaccination (July/August in the northern hemisphere, or January/February in the southern hemisphere) may be considered; this approach may reduce risk for influenza illness among their infants during the first months after birth, when they are too young to receive the influenza vaccine [1,27].

Vaccine selection – Pregnant patients may be immunized with any licensed inactivated influenza vaccine (IIV) or recombinant influenza vaccine [1]. (See "Seasonal influenza vaccination in adults".)

Pregnant patients should not be immunized with a live-attenuated influenza vaccine (LAIV) due to concerns about the safety of a live vaccine administered during pregnancy [1]. It is not necessary for pregnant patients to avoid contact with others who have recently received LAIV. Postpartum patients may receive a live virus vaccine. (See "Immunizations during pregnancy", section on 'Live vaccines'.)

Issues related to influenza vaccination for individuals with egg allergy are discussed separately. (See "Influenza vaccination in persons with egg allergy".)

Increasing uptake – Vaccine uptake remains suboptimal [43]. In one survey of pregnant individuals in the United States from 2022 to 2023, only 47 percent reported receiving the influenza vaccine [44]. Vaccination rates in pregnant patients in other countries are also suboptimal [45]. The most commonly reported reason for not receiving influenza vaccination in pregnancy is the belief that the vaccine is not effective [46]. Rates of influenza vaccination during pregnancy are highest when the provider recommends and offers the vaccine [47].

Efficacy — Influenza vaccination plays a key role in reducing the risk of maternal influenza illness and hospitalization, improving pregnancy outcomes, and protecting the infant for several months after birth.

Reducing maternal influenza illness and hospitalization – Influenza vaccination plays a key role in reducing the risk of maternal influenza illness. Pregnant patients achieve seroprotection at rates similar to nonpregnant patients [26,48], although there may be some differences in the antibody response of pregnant patients to influenza vaccine compared with nonpregnant patients [49].

In a systematic review and meta-analysis of cohort studies of vaccination for preventing influenza in healthy adults, H1N1 vaccines reduced the risk of influenza-like illness in pregnant patients by 89 percent (95% CI 79-94) and the seasonal vaccine reduced the risk of influenza-like illness in pregnant patients by 24 percent (95% CI 11-35) [50]. Reductions in influenza-like illness have also been reported in randomized trials and large case-control study not reported in this systematic review [51-53].

Influenza vaccination also reduces the risk of influenza-related hospitalizations. In a study including pregnant patients from hospitals in Australia, Canada, Israel, and the United States between 2010 and 2016, the influenza vaccine was 40 percent effective (adjusted vaccine effectiveness 40 percent, 95% CI 12-59 percent) in preventing laboratory-confirmed influenza-associated hospitalization [54].

Improving pregnancy outcome – Influenza vaccination improves pregnancy outcomes. In a systematic review and meta-analysis of observational studies on the effect of maternal influenza immunization on stillbirth and pregnancy loss, influenza vaccination was associated with a reduction in risk of stillbirth (relative risk [RR] 0.73, 95% CI 0.55-0.96) but not pregnancy loss [55]. Others have reported influenza vaccination is associated with a reduced risk for small-for-gestational-age (SGA) infants and preterm delivery [52,56-60] and an increase in birth weight [56].

Infant protection – In addition to protecting the pregnant patient, influenza vaccination during pregnancy protects the infant for several months after birth [52,61-69]. In the systematic review and meta-analysis of cohort studies discussed above, newborns of vaccinated patients had a 41 percent (95% CI 6-63) reduction in laboratory-confirmed influenza [50]. Similarly, in a random effects meta-analysis of two randomized trials including 5742 participants in South Africa and Nepal, maternal influenza vaccination was associated with a 34 percent overall reduction of laboratory confirmed influenza among infants (95% CI 15-50 percent) [70].

Antenatal maternal immunization induces substantial levels of anti-influenza-specific serum immunoglobulin G (IgG), which are actively transferred across the placenta to the fetus [71], and anti-influenza-specific IgA in breast milk, which is transferred to the infant during lactation [72]. Thus, antenatal maternal vaccination is an effective strategy for reducing influenza-related morbidity and mortality among infants, who are at increased risk for severe influenza illness and not eligible for vaccination until six months of age because they fail to mount an adequate immune response [73,74]. Maternal vaccine may also reduce hospitalizations for all-cause acute lower respiratory tract infection before three months of age [75].

However, passive protection afforded by maternal influenza vaccination declines significantly before the infant is eligible for influenza virus vaccination. In a randomized trial of 1026 infants of patients who received trivalent IIV during pregnancy and 1023 infants of patients who received a placebo, the vaccine's efficacy against polymerase chain reaction (PCR)-confirmed influenza illness was approximately 86 percent in infants ≤8 weeks of age and 25 to 30 percent in infants 8 to 24 weeks of age [66]. The percentage of infants with hemagglutination inhibition antibody titers ≥1:40 to the influenza vaccine strains targeted by the vaccine was ≥56 percent in the first week and fell to <10 percent at 24 weeks of age. Others have observed similar decreases in vaccine efficacy over time [67].

It is possible that maternal immunization in the third trimester would improve passive protection for the newborn [76], as with Tdap; however, delaying maternal immunization places the mother at risk for influenza and its sequelae (maternal and fetal) and is not recommended.

Safety — Although pregnant patients often have concerns about the safety of vaccines for their fetuses, multiple studies have not shown an increased risk of complications associated with administration of IIVs to pregnant patients compared with the general population [26,50,52,77-95]. Similarly, no significant adverse pregnancy or fetal outcomes have been observed among pregnant patients who have received influenza vaccination. In a systematic review and meta-analysis including seven studies, patients who received influenza vaccine compared with no vaccination had a lower likelihood of stillbirth (RR 0.73, 95% CI 0.55-0.96) but a similar rate of pregnancy loss [55].

Although influenza vaccines that contain adjuvants (substances that boost the immune response and potentially provide longer-lasting and broader protection against antigenically-drifted viruses) are only approved in the United States for use in individuals ≥65 years of age, experience from Europe provides limited but reassuring data on the safety of adjuvant-containing influenza vaccines administered to pregnant patients [96-98].

There is no evidence that vaccines that contain thimerosal are harmful to the children of patients who received thimerosal-containing vaccines during pregnancy. However, thimerosal-free formulations of the seasonal influenza vaccine are available. (See "Standard childhood vaccines: Caregiver hesitancy or refusal", section on 'Influenza vaccine misinformation'.)

Role of antiviral prophylaxis — Antiviral drugs may be useful adjunctive tools for prevention of influenza in certain circumstances but should not be used as a substitute for vaccination.

The role of pre-exposure and postexposure prophylaxis for prevention of influenza is discussed separately. (See "Seasonal influenza in adults: Role of antiviral prophylaxis for prevention".)

SOCIETY ALGORITHM LINK — The American College of Obstetricians and Gynecologists (ACOG) and Society for Maternal-Fetal Medicine have jointly published an algorithm for assessment and treatment of pregnant patients with influenza-like illness.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Immunizations in adults" and "Society guideline links: Seasonal influenza vaccination" and "Society guideline links: Respiratory disease in pregnancy".)

SUMMARY AND RECOMMENDATIONS

General principles – Pregnant patients with seasonal influenza are more likely to be hospitalized and admitted to an intensive care unit and have a higher mortality compared with the general population. Maternal influenza also increases the risk of adverse fetal outcomes (eg, congenital anomalies, preterm birth, fetal death). (See 'Effects on pregnancy' above.)

Clinical manifestations – Clinical manifestations of influenza in pregnant and postpartum patients are similar to those in the general population and include an abrupt onset of fever, nonproductive cough, and myalgia. Other nonspecific symptoms include malaise, sore throat, nausea, nasal congestion, and headache. (See 'Clinical manifestations' above.)

Diagnosis – The diagnosis of uncomplicated influenza should be suspected in patients with abrupt onset of fever, cough, and myalgia when influenza virus is circulating (in the northern hemisphere, typically September to April; in the southern hemisphere, typically April to September). A positive test for influenza virus confirms the diagnosis. However, a negative test for influenza virus cannot rule out infection, especially if the test does not have adequate sensitivity or if the specimen was collected >4 days after illness onset. (See 'Diagnosis' above.)

Management

Infection control – General issues related to infection control measures for prevention of seasonal influenza (eg, hand and respiratory hygiene, droplet precautions) are the same as for nonpregnant patients and presented in the table (table 1). (See 'Infection control measures' above.)

Pregnancy and recently postpartum patients – For pregnant and postpartum patients (within two weeks of delivery or pregnancy loss) with suspected or confirmed influenza, we recommend influenza antiviral treatment as early as possible, regardless of vaccination status (Grade 1C). Treatment should not be withheld while awaiting results of diagnostic testing or in situations in which testing is not performed. (See 'Antiviral treatment' above.)

-Antiviral selection – We suggest treatment with oseltamivir (Grade 2C). Alternative agents include peramivir or zanamivir; dosing is summarized above. Baloxavir, however, is not generally used for pregnant or postpartum patients given lack of safety and efficacy data. (See 'Antiviral agents' above.)

-Symptom management – Fever should be treated with acetaminophen. (See 'Symptom management' above.)

Newborns – Asymptomatic newborns (born in the hospital with infection control precautions) should be considered exposed, not infected. These newborns may receive care in the nursery using standard precautions and should be observed for signs of infection; routine use of antiviral prophylaxis is not recommended. (See 'Newborns' above.)

Household contacts and infant caregivers – All eligible household members and infant caretakers should be vaccinated against influenza virus. Issues related to antiviral prophylaxis for household members and infant caretakers who have close contact with an individual with influenza are discussed separately. (See 'Household contacts and infant caregivers' above and "Seasonal influenza in adults: Role of antiviral prophylaxis for prevention", section on 'Postexposure antiviral prophylaxis'.)

Prevention (See 'Vaccination' above.)

We recommend influenza virus vaccination for all patients who are pregnant or will be pregnant or postpartum during influenza season (Grade 1A), regardless of pregnancy trimester. Issues related to timing are discussed above. Influenza vaccination during pregnancy provides maternal protection and also may reduce risk for influenza illness among infants during their first six months of life (when they are too young to receive the influenza vaccine).

Such patients should be immunized with any licensed inactivated influenza vaccine (IIV) or recombinant influenza vaccine; they should not be immunized with a live-attenuated influenza vaccine (LAIV). No increased risk of adverse pregnancy or fetal outcomes have been observed among pregnant patients who have received influenza vaccination.

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Topic 15870 Version 109.0

References

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