With Increasing Vaccination Reluctance, Does Rubella Immunity Predict Rubeola Immunity Well Enough?

<b><i>Introduction:</i></b> Recent outbreaks of measles (rubeola) have underscored the importance of immunity and vaccination. By late 2019, measles had a decade of rising cases, culminating in widespread outbreaks. The COVID-19 pandemic exacerbated this event due to disruptions in healthcare services. Unlike rubella, rubeola testing is not routinely performed in the United States. The objective of this study is to evaluate rubella and rubeola immunization status and the potential concordance between rubella and rubeola immunity. <b><i>Methods:</i></b> This was a retrospective study of patients treated at a single reproductive endocrinology clinic between January 1, 2015, and March 31, 2019. Patients were excluded if rubella or rubeola results were missing. Results were classified as immune (positive) or nonimmune (negative or indeterminate). Logistic regression analysis was used to predict immunity status based on factors such as age, body mass index, and race. <b><i>Results:</i></b> Of 524 cases, 387 (73.9%) patients were immune to both rubella and rubeola while 86 (16.4%) exhibited immunity to rubella only. There was a statistically significant difference in concordance between rubeola and rubella immunity (<i>p</i> = 0.0014) with more immune to rubella (90.3%, <i>n</i> = 473) compared with rubeola (72.2%, <i>n</i> = 415). Nearly two-thirds of patients reported receiving the measles, mumps, and rubella (MMR) vaccine (<i>n</i> = 361, 68.9%). Most patients were white/Caucasian (<i>n</i> = 442, 84.45%), obese or morbidly obese (<i>n</i> = 247, 47.1%), and >30 years old (<i>n</i> = 276, 52.7%). <b><i>Conclusions:</i></b> Rubella immunization status does not definitively predict rubeola immunity. Given increasing risk of measles outbreaks in the United States, prenatal testing for rubeola could prove beneficial.