Small Response Gain With Double-Dose Flu Shot in Pregnant Women With HIV

By Anne Harding

January 16, 2020

NEW YORK (Reuters Health) - Doubling the dose of influenza vaccine for pregnant women with HIV moderately improves immunogenicity compared to a single flu shot, but response remains well below that of pregnant women without HIV, a clinical trial shows.

"More immunogenic vaccines are needed for pregnant women living with HIV to enhance transplacental transfer of vaccine-induced protective antibodies to their newborn infants," Dr. Marta C. Nunes of Chris Hani Baragwanath Hospital in Johannesburg, South Africa, and colleagues conclude in The Lancet HIV.

Previous research in South Africa has found that pregnant women infected with HIV have lower antibody titers and are less likely to seroconvert after influenza vaccination than HIV-negative pregnant women, Dr. Nunes and her team note.

The researchers randomly assigned 800 pregnant women with HIV to receive a single dose of trivalent inactivated influenza vaccine, a double dose, or two doses a month apart. Women were recruited from antenatal clinics in Soweto, a township of 1.2 million people near Johannesburg, where 29% of pregnant women are HIV-positive.

At one month, seroconversion rates for the three vaccine strains were 18%-49% in the single-dose group, 29%-65% for the double-dose group, and 23%-52% with two doses. Rates were significantly higher for the double-dose group compared to the single-dose group, while they were similar for the single- and two-single-dose groups.

While immunogenicity was "slightly improved" with the double dose, it remained lower than the 92% seroconversion rate in a 2011 study of HIV-negative women who received a single dose, the authors note.

Women in the double-dose group were also more likely to have titers of at least 1/40 to each of the vaccine strains compared to the single-dose group. However, there were no differences among women or infants across the three groups in the incidence of PCR-confirmed influenza.

"Despite lower humoral responses to influenza vaccination in individuals living with HIV, inactivated influenza vaccine is efficacious, and vaccination of this vulnerable population should continue," the authors write.

The authors should be given "a huge amount of credit" for the current study, Dr. Sharon Nachman of Stony Brook University in New York told Reuters Health in a phone interview. Dr. Nachman, who wrote an editorial published with the study, chairs the International Maternal Pediatric Adolescent AIDS Clinical Trials (IMPAACT) Network.

The results show that "you can do studies in pregnant women with HIV incredibly successfully," she said. "Women understood what the study was about, and they enrolled in a timely fashion."

Clinical trials almost invariably exclude pregnant women, Dr. Nachman said, noting that the US Food and Drug Administration currently only requires that studies be done in adults.

"We all need a better flu vaccine -- pregnant women are not excluded from that 'everybody,'" she added. "I am only hopeful that when we start studying some of these new vaccines, pregnant women are included, not as part of phase 4 but earlier."

The study was funded by the Bill & Melinda Gates Foundation.

SOURCE: and The Lancet HIV, online January 3, 2020.