When to Get the Influenza Vaccine During Pregnancy?【supervised by doctor】

What Happens When Pregnant Women Get the Flu?

When pregnant women contract influenza, various reported impacts include an increased susceptibility to various complications. Specific effects on the fetus may manifest as congenital abnormalities such as neural tube defects and cardiac malformations. Additionally, there is a known association with adverse outcomes such as spontaneous abortion, preterm birth, low birth weight, and intrauterine growth restriction (infant’s weight below the 10th percentile for gestational age).

In terms of maternal effects, during the H1N1 influenza pandemic in 2009, it was observed that pregnant women had a higher hospitalization rate compared to non-pregnant individuals. This trend was noted not only in Japan but also internationally, with reported cases of maternal deaths.

Therefore, both the Ministry of Health, Labour and Welfare and the Japanese Society for Vaccinology recommend influenza vaccination domestically. The Japan Society of Obstetrics and Gynecology also encourages pregnant women to consult with healthcare professionals, receive explanations of the benefits from physicians, and make decisions regarding vaccination.

About Influenza Vaccination

At present, influenza vaccine safety and efficacy have not been sufficiently confirmed for newborns (under 6 months old). Therefore, vaccination is not performed for infants within this age group. To minimize the risk of influenza infection for infants up to 6 months old, it is observed that receiving the influenza vaccine during pregnancy or after childbirth is effective.

By choosing not to receive the influenza vaccine, there is a potential for these impacts to become more likely. Additionally, during the outbreak of novel influenza strains, many maternal deaths were reported overseas, while Japan did not report maternal deaths. This is attributed to the appropriate response of Japan’s Ministry of Health, Labour and Welfare and the Japan Society of Obstetrics and Gynecology, prioritizing the vaccination of pregnant women at high risk of severe complications and early administration of antiviral medications.

Recent reports also suggest that influenza vaccine administration may reduce the incidence of respiratory diseases during the first six months after birth. This implies a potential additional benefit of the influenza vaccine, not only preventing influenza but also respiratory diseases in the postnatal period.

Therefore, both in Japan and globally, influenza vaccination for pregnant women, either during pregnancy or after childbirth, is recommended to prevent influenza for both mothers and infants.

Is it Safe to Get the Influenza Vaccine During Pregnancy?

It is possible to receive the influenza vaccine during pregnancy, and there are no specific restrictions on the timing of vaccination.

However, if you are taking certain immunosuppressive medications or medications related to cancer treatment (such as drugs for rheumatoid arthritis or chemotherapy), which are approved in the country, there is a potential for interactions that could reduce the effectiveness of the influenza vaccine. In such cases, it is advisable to consult with your attending physician before getting vaccinated.

Is it Safe to Get the Influenza Vaccine While Breastfeeding?

It is possible to receive the influenza vaccine while breastfeeding.

It has been established that getting the influenza vaccine during breastfeeding does not adversely affect the safety of breast milk.

Effects of the Influenza Vaccine

The potential effects of the influenza vaccine are similar to other vaccine administrations. This includes local reactions at the injection site, such as redness, pain, and swelling, as well as systemic reactions like fever, chills, headache, fatigue, joint pain, and muscle aches. However, these side effects are generally considered to be temporary and typically resolve within 2 to 3 days.

When to Get the Influenza Vaccine During Pregnancy?【supervised by doctor】

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Pregnant Women/Maternal Effects

As mentioned earlier, there is a possibility of local and systemic reactions appearing, but these are generally expected to disappear within a few days. Some influenza vaccines contain ethylmercury (thimerosal) as a preservative, which may raise concerns. However, thimerosal is found not only in influenza vaccines but also in other vaccines. The concentration in thimerosal-containing formulations is extremely low, and it is considered to have no impact on the fetus or developing baby.

It’s worth noting that there have been reports of hypersensitivity reactions (fever, rash, hives, erythema, itching, etc.) following the administration of thimerosal-containing formulations.

While there were concerns about a potential link between thimerosal and autism after 2004, current evidence does not support this connection, and the World Health Organization (WHO) has issued statements negating such associations. The administration of influenza vaccines containing thimerosal as a preservative is considered safe for pregnant women.

Although thimerosal-free influenza vaccines are recommended for pregnant women, they are slightly more expensive than the regular vaccines. It is advisable to consult with your healthcare provider before vaccination and consider their recommendations for vaccine selection.

Fetal Effects

Influenza vaccines that use live viruses are contraindicated for pregnant women due to considerations of fetal impact.

Breast Milk

Vaccination with the influenza vaccine during breastfeeding is known not to affect the safety of breast milk. Therefore, receiving the influenza vaccine while breastfeeding is possible.

Mothers immediately after childbirth and infants under 6 months old are more likely to experience severe symptoms of influenza compared to the general population.

Therefore, getting vaccinated with the influenza vaccine during breastfeeding is considered desirable for both the mother and the child.

When to Get the Influenza Vaccine During Pregnancy?【supervised by doctor】

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Main Side Effects of the Influenza Vaccine

It is noted that there is a possibility of local reactions at the injection site, such as redness, pain, and swelling, as well as systemic reactions like fever, chills, headache, fatigue, joint pain, and muscle aches, following administration of the influenza vaccine. These side effects are generally expected to disappear within 2 to 3 days.

When to Get the Influenza Vaccine

Before Pregnancy

Influenza vaccination is possible as usual.

There have been no reports indicating reduced fertility or pregnancy interruptions associated with the administration of inactivated influenza vaccines. Therefore, to prevent the potential impact of influenza infection on both the mother and the child, it is recommended to receive the influenza vaccine starting before pregnancy.

Early Pregnancy (Around 0-3 Weeks Pregnant)

Influenza vaccination is possible, similar to before pregnancy.

Considering that the benefits of receiving the influenza vaccine are believed to outweigh potential risks, its implementation is recommended.

Early Pregnancy (Up to 13 Weeks 6 Days Pregnant)

Influenza vaccination is possible during pregnancy. Similar to before pregnancy and during the early stages of pregnancy, vaccination is considered advisable and recommended for prevention.

NIPT (Non-Invasive Prenatal Testing) is available from early pregnancy

At Hiro Clinic NIPT, NIPT is available as soon as pregnancy is confirmed through ultrasound examination. NIPT is a prenatal test that examines the risk of chromosomal abnormalities in the fetus.

While NIPT is available to anyone who has confirmed pregnancy through ultrasound examination, it is recommended that those planning to undergo amniocentesis in the case of a positive result receive NIPT by 14 weeks of gestation.

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Mid-Pregnancy (14 Weeks 0 Days to 27 Weeks 6 Days)

During the mid-pregnancy period, the rates of birth defects and miscarriage are considered to remain unchanged from the early stages of pregnancy, and vaccination is recommended. Additionally, the effectiveness of the influenza vaccine is generally observed from about 2 weeks after administration and lasts for approximately 5 months. Therefore, it is believed that vaccination during the late pregnancy period until childbirth can be effective in preventing influenza infection.

Late Pregnancy (28 Weeks and Beyond)

In the late stages of pregnancy, like any other period during pregnancy, influenza vaccination is possible and recommended. While there may be some inconvenience during clinic visits for preventive vaccination, it is recommended to receive the influenza vaccine during both pregnancy and breastfeeding periods due to the recognized impact of infection during these periods.

Where Can Pregnant Women Get the Influenza Vaccine?

If the hospital offers regular influenza vaccine administration, you can receive the vaccination there. Confirm whether the desired vaccine is available and consult with your obstetrician or primary care physician before getting vaccinated.

Things to Consider When Pregnant Women Receive the Influenza Vaccine

It is advisable to choose the vaccination date based on your health condition, as there is a possibility of experiencing stronger side effects compared to the general population.

Preparation Until the Day Before

It’s important to consult with your obstetrician or primary care physician about any questions or concerns you may have. For both your well-being and the baby’s, consider convenient and low-stress transportation methods for traveling between the hospital and home.

Items to Bring on the Day

Because there are medications that require caution when used concurrently, it’s recommended to bring your medication notebook or a note detailing the medications you usually take.

Post-Vaccination Care

Because there is a possibility of side effects for several days, it is advisable to rest as much as possible. If possible, seek assistance from your family or those around you with household chores.

Vaccination for Cohabiting Family Members

The impact of influenza infection is considered significant for both the mother and the child, and recommendations for the prevention of influenza are emphasized by organizations such as the Ministry of Health, Labour and Welfare, the Japan Pediatric Society, and the Japan Society of Obstetrics and Gynecology. Depending on the situation of cohabitating family members, there may be cases where influenza vaccination is not possible, but it is reassuring to have them vaccinated whenever possible.

Conclusion

From before pregnancy to breastfeeding, we have provided information on the impact of influenza infection on both mother and child, as well as important points regarding influenza vaccine itself and vaccination. Extra caution is considered necessary for pregnant women.

Influenza vaccination is possible even before pregnancy. Please consider discussing influenza vaccine administration with your obstetrician or primary care physician.