An alert from U.S. health authorities about recipients of COVID-19 vaccines recording false positive results for syphilis has been misconstrued online.
According to some social media users, the Food and Drug Administration (FDA) admitted in December to “vaccine-induced syphilis” caused specifically by COVID-19 shots (here and here).
One user joked: “Totally normal…I’m sure it’s nothing”, while others replied with tweets suggesting vaccines contained the sexually transmitted infection (STI) (here).
On Dec. 17, the FDA first circulated a letter to healthcare and laboratory workers warning of the possibility of false-positive syphilis results in vaccinated people when specifically using the ‘Bio-Rad Laboratories BioPlex 2200 Syphilis Total & RPR kit’ (here).
The same letter said false-positives could be seen up to five months after inoculation in some individuals and urged anyone using the RPR kit to try a different type of test for confirmation. However, it also highlighted: “COVID-19 vaccines do not cause syphilis.”
The U.S. Centers for Disease Control and Prevention (CDC) later distributed its own letter to amplify the FDA’s alert.
It added that, historically, false-positive RPR test results for syphilis have been seen in people with systemic infections unrelated to the STD, such as tuberculosis, rickettsial diseases, and endocarditis, as well as during pregnancy and following other immunizations. One example of the latter is the smallpox vaccine (here). This is due to the RPR test measuring nontreponemal antibodies, which are not exclusive to syphilis (bit.ly/35q1sYj).
The CDC letter also notes that reactive RPR results should always be confirmed using a different type of test, per its 2021 STI Treatment Guidelines (bit.ly/3hvwsbI).
“This is, in part, because of the above-mentioned issue: false-positive nontreponemal test results can be associated with multiple medical conditions and factors unrelated to syphilis,” the CDC letter says.
“According to FDA’s alert, treponemal testing for syphilis does not appear to be impacted by this issue.”
Reuters Fact Check has previously addressed other claims about STIs and COVID—19 vaccines here
Missing Context. The FDA and CDC letters have been misconstrued. An RPR test can sometimes give false positive results due to the type of antibody it is measuring. Therefore, confirmation is necessary with another type of test.
This article was produced by the Reuters Fact Check team. Read more about our fact-checking work here.
Our Standards: The Thomson Reuters Trust Principles.