by Anne Eglash MD, IBCLC, FABM
Which flu vaccine is safer and more effective during breastfeeding? Sorry folks, but it is time to think about flu season once again! Last year in the USA the Center for Disease Control recommended against the use of the nasal flu vaccine, which is a live attenuated (weakened) influenza vaccine (LAIV), because there were concerns that it would not be effective against the expected strains of influenza. Instead, the inactivated (not live) influenza vaccine (IIV) in shot form was the preferred flu vaccine. In prior years, most healthy people between the ages of 2 and 50 were offered either the nasal LAIV or the IIV shot. The nasal LAIV was thought to be more effective for and certainly preferred by most children. Many breastfeeding mothers declined the nasal LAIV for themselves, worried that the live attenuated influenza virus would be transmitted to their newborns.
Pregnant women are encouraged to take the IIV (not the LAIV) to protect themselves from influenza, and to transmit anti-influenza antibodies thru the placenta to their newborns, who cannot receive the flu vaccine until 6 months of age. There has been little research comparing the IIV and LAIV for breastfeeding mothers, regarding transmission of anti-influenza antibodies in the breastmilk. In addition, the transmission of the live attenuated virus into breastmilk and passage to the infant has not been well studied.
A recently published well-designed randomized controlled trial with 248 breastfeeding mothers investigated the safety of the nasal LAIV and the effectiveness of the nasal LAIV vs the IIV shot when these vaccines were given to the mother. They cultured infant noses and breastmilk for evidence of the influenza from the nasal LAIV. They also checked the mother’s antibody response to both types of vaccines.
What do you think the researchers found regarding the safety and effectiveness of the 2 types of flu vaccines? (choose 1 or more)
- Among breastfeeding infants whose mothers were given the nasal LAIV, 1% tested positive for the vaccine virus from their nasal swabs.
- 25% of mothers given the nasal LAIV had the virus in her breastmilk.
- The infants who tested positive for the vaccine virus from mom’s LAIV did not display illness.
- There was no difference in the influenza IgG antibodies in breastmilk between the LAIV and the IIV.
- The researchers recommend the IIV over the LAIV for breastfeeding mothers because the IIV produces higher maternal serum antibody levels.
- The live weakened virus in the nasal LAIV has been shown to transform into to a stronger influenza virus that can make people sick.
See the Answer
The correct answers are A, C, E (not B, D, or F)
Vaccine. 2018 Jul 25;36(31):4663-4671. doi: 10.1016/j.vaccine.2018.06.036. Epub 2018 Jun 28.
Randomized trial comparing the safety and antibody responses to live attenuated versus inactivated influenza vaccine when administered to breastfeeding women
Brady RC, Jackson LA, Frey SE, Shane AL, Walter EB, Swamy GK, Schlaudecker EP, Szefer E, Wolff M, McNeal MM, Bernstein DI, Steinhoff MC.
Live attenuated influenza vaccine (LAIV) and inactivated influenza vaccine (IIV) are both licensed for administration to nursing mothers. Little is known about the potential for transmission of LAIV viruses from the mother to the infant and the comparative breast milk antibody responses to LAIV and IIV.
We performed a randomized, double-blind study comparing the immunogenicity of LAIV to IIV when administered to nursing mothers. The safety of LAIV to IIV in women and their infants was also compared. Women received LAIV + intramuscular placebo, or IIV + intranasal placebo on Day 0. Breast milk and nasal swabs (from women and infants) were collected on Days 0, 2, and 8 for detection of LAIV. Breast milk and serum antibody responses were measured at Days 0 and 28. The primary hypothesis was that LAIV would provide superior induction of breast milk IgA responses to influenza as compared to IIV when administered to nursing mothers.
Breast milk IgG, breast milk IgA (H1N1 only), serum hemagglutination inhibition (HAI), and serum IgG responses were significantly higher following administration of IIV compared to LAIV. Receipt of either LAIV or IIV was safe in women and their infants. One (1%) LAIV recipient transmitted vaccine virus to her infant who remained well. No influenza virus was detected in breast milk.
Breast milk and serum antibody responses were higher for IIV compared to LAIV. LAIV and IIV were safe for nursing women but there was one (1%) possible transmission of LAIV to an infant. This study suggests that IIV may be the preferred vaccine for nursing mothers.
Milk Mob Comment by Anne Eglash MD, IBCLC, FABM
The researchers found that none of the mothers given nasal LAIV had vaccine virus in their breastmilk. Although 1% of infants carried the flu vaccine virus in their nose after maternal administration of the nasal LAIV, none of the infants showed signs of clinical illness. The authors also point out that there have been no cases of the attenuated vaccine virus turning into a stronger virus causing clinical illness.
The researchers recommend the flu shot over the nasal flu vaccine because the IgG antibody responses to the vaccine in mom’s serum and breastmilk are higher.
I have plenty of adults in my practice who are needle shy or needle phobic, and are more likely to take the influenza vaccine by nose than by shot. Based on this research it appears that breastfeeding mothers can be advised that if she prefers the nasal live attenuated influenza vaccine, it is safe for her and her infant. It just might not be as effective as the flu shot.