HealthDay News — The trivalent inactivated influenza vaccine (IIV3) provides protection against confirmed influenza in HIV-negative and HIV-positive pregnant women and in infants not exposed to HIV for up to 24 weeks after birth, according to researchers.

“There are limited data on the efficacy of vaccination against confirmed influenza in pregnant women with and those without human immunodeficiency virus (HIV) infection and protection of their infants,” wrote Shabir A. Madhi, MD, PhD, from the Chris Hani-Baragwanath Hospital in Bertsham, South Africa, and colleagues in The New England Journal of Medicine.

To determine the efficacy of IIV3 in pregnant patients, the inspectors conducted double-blind, randomized trials of IIV3 in pregnant women diagnosed with HIV (n=193) and in uninfected pregnant women(n=2,116). Patients were assigned to receive IIV3 or placebo and were monitored until 24 weeks after birth.

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One month after vaccination in both cohorts, the seroconversion rates and the proportion of patients with hemagglutination inhibition (HAI) titers of ≥1:40 were higher among IIV3 recipients, than among placebo recipients. Higher HAI titers were also seen in newborns of IIV3 recipients compared with newborns of placebo recipients.

The attack rate for reverse-transcriptase-polymerase-chain-reaction-confirmed influenza was 3.6% among both HIV-uninfected placebo recipients and their infants. Among HIV-uninfected IIV3 recipients and their infants, the attack rates were 1.8% and 1.9%, respectively, yielding vaccine-efficacy rates of 50.4% and 48.8%, respectively.

The attack rate for HIV-infected placebo recipients was 17.0%, whereas the rate for HIV-infected IIV3 recipients was 7.0%, yielding a vaccine-efficacy rate for these IIV3 recipients of 57.7%. Vaccination was found to be effective in HIV-unexposed infants up until 24 weeks after birth.

“Influenza vaccine was immunogenic in HIV-uninfected and HIV-infected pregnant women and provided partial protection against confirmed influenza in both groups of women and in infants who were not exposed to HIV,” concluded the researchers.


  1. Madhi SA et al. New England Journal of Medicine. 2014; doi: 10.1056/NEJMoa1401480

Disclosures:Several authors disclosed financial ties to the pharmaceutical industry.