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Vaccination against meningococcal serogroup B may also provide modest protection against gonorrhea, evidence from the U.S. and Australia showed.

According to surveillance records from New York City and Philadelphia, complete vaccination with the four-component meningococcal serogroup B vaccine (MenB-4C; Bexsero) provided 40% protection against gonorrhea infection compared with no vaccination (adjusted prevalence ratio [APR] 0.60, 95% CI 0.47-0.77, P<0.0001), reported Winston Abara, MD, of the CDC, and colleagues.

In addition, partial vaccination offered 26% protection against gonorrhea compared with no vaccination (APR 0.74, 95% CI 0.63-0.88, P=0.0012), they noted in

These findings "could have a major impact on prevention and control of the disease," said Abara in a statement.

"Clinical trials focused on the use of [MenB-4C] against gonorrhea are needed to better understand its protective effects and could also offer important insights towards the development of a vaccine specifically for gonorrhea," he added.

Treating gonorrhea has posed a particular problem, as Neisseria gonorrhoeae has developed resistance to first-line antibiotics, as well as reduced susceptibility to cephalosporins. While there is no vaccine against gonorrhea, prior research has found that mass vaccination campaigns against meningitis B with an "outer membrane vesicle vaccine" were tied to a lower likelihood of gonorrhea infection.

MenB-4C is one of the two vaccines against meningococcal serogroup B licensed in the U.S., and the CDC's Advisory Committee on Immunization Practices (ACIP) recommends that adolescents and young adults ages 16 to 23 receive the vaccine based on "shared clinical decision-making."

For this study, Abara's group examined surveillance data from New York City and Philadelphia public health departments on diagnosed gonorrhea and chlamydia infections in this younger population from January 2016 through December 2018. Cases were linked to immunization registry records to determine MenB-4C vaccination status, including date and number of doses received. The group then determined if the sexually transmitted infection occurred before or after the vaccination date.

Overall, 109,737 individuals ages 16 to 23 (65.5% women, 38.7% Black) in the immunization registries were diagnosed with gonorrhea or chlamydia, 7,962 of whom received at least one dose of MenB-4C (52% received one dose, 47% received two doses, and under 1% received three doses).

Of the reported sexually transmitted infections, 75% were chlamydia, 11% were gonorrhea, and 15% were gonorrhea and chlamydia co-infections. About 2% of infections occurred after the complete vaccination series, and 4% occurred after a partial vaccination series.

Interestingly, vaccination was not protective against gonorrhea and chlamydia co-infection.

Vaccination Conferred Protection in Australia, Too

A found that the estimated two-dose effectiveness of MenB-4C was 32.7% (95% CI 8.3-50.6) against gonorrhea, reported Helen Marshall, MD, of Women's and Children's Hospital in Adelaide.

Over 2 years, 53,356 adolescents and young adults received at least one dose of MenB-4C vaccine, and 46,083 received two doses.

Marshall and team estimated MenB-4C effectiveness against gonorrhea using data from 512 individuals with gonorrhea infection born from February 1998 to February 2005 and 3,140 age-matched controls with chlamydia infection.

Both studies used chlamydia controls to calculate vaccine effectiveness and both used laboratory-confirmed diagnoses and established vaccination registries, noted Jason Ong, MBBS, PhD, of Monash University in Melbourne, Australia, and colleagues in an .

However, they pointed out that 15% of data on sexually transmitted infections in Abara's study could not be linked to vaccination data, and the "quality of the linkage process" was not clear in the study by Marshall's group.

"Many unknowns also remain related to the potential duration of vaccine protection, vaccine effect on repeat gonococcal infections, effect of co-infection with chlamydia and other pathogens on vaccine response, the effect of vaccination coverage, and anatomic site-specific vaccine effectiveness," Ong and colleagues wrote. "It is still essential to establish the causative mechanisms of the observed cross-protection and how to translate this to the development of a gonococcal vaccine."

They stressed that the effectiveness of a gonococcal vaccine for men who have sex with men "is sensitive to its effect on reducing oropharyngeal infections."