Spatial Clustering of Vaccine Exemptions on the Risk of a Measles Outbreak

OBJECTIVES Areas of increased school-entry vaccination exemptions play a key role in epidemics of vaccine-preventable diseases in the United States. California eliminated nonmedical exemptions in 2016, which increased overall vaccine coverage but also rates of medical exemptions. We examine how spatial clustering of exemptions contributed to measles outbreak potential pre- and postpolicy change. METHODS We modeled measles transmission in an empirically calibrated hypothetical population of youth aged 0 to 17 years in California and compared outbreak sizes under the observed spatial clustering of exemptions in schools pre- and postpolicy change with counterfactual scenarios of no postpolicy change increase in medical exemptions, no clustering of exemptions, and lower population immunization levels. RESULTS The elimination of nonmedical exemptions significantly reduced both average and maximal outbreak sizes, although increases in medical exemptions resulted in more than twice as many infections, on average, than if medical exemptions were maintained at prepolicy change levels. Spatial clustering of nonmedical exemptions provided some initial protection against random introduction of measles infections; however, it ultimately allowed outbreaks with thousands more infections than when exemptions were randomly distributed. The large-scale outbreaks produced by exemption clusters could not be reproduced when exemptions were distributed randomly until population vaccination was lowered by >6 percentage points. CONCLUSIONS Despite the high overall vaccinate rate, the spatial clustering of exemptions in schools was sufficient to threaten local herd immunity and reduce protection from measles outbreaks. Policies strengthening vaccine requirements may be less effective if alternative forms of exemptions (eg, medical) are concentrated in existing low-immunization areas.

Safety of Live-Attenuated Measles, Mumps, and Rubella Vaccine Administered Within 2 Years of Hematopoietic Cell Transplant

Background Measles, mumps, and rubella (MMR) vaccine is a live-attenuated vaccine usually contraindicated within the first 2 years of hematopoietic cell transplant (HCT). The objective of this study was to assess the safety of MMR vaccine when administered within 2 years of HCT. Methods We conducted a retrospective review of patients who received MMR vaccination within 2 years of an autologous or allogeneic HCT, mostly in the context of the 2019 measles outbreak. Adverse reactions were collected for 42 days postvaccination, and all hospitalizations and deaths following vaccination were reviewed. Results A total of 129 patients (75 autologous and 54 allogeneic HCT) were vaccinated 300–729 days after HCT (median, 718 days), and 39 (30%) of these were vaccinated earlier than 23 months post-transplant. Ten adverse reactions in 7 patients (5%) were identified within 42 days of vaccination: 6 respiratory tract infections (3 with fever) and 1 rash. The rash was seen in a 37-year-old female who had an allogeneic HCT 542 days before vaccination. She presented with a centrifugal maculopapular rash, confirmed to be caused by the vaccine strain rubella virus. She fully recovered. No other vaccine-associated illness was identified in the cohort after a median follow-up of 676 days. Conclusions MMR vaccine appears to be well tolerated in select HCT recipients when given between 300 and 729 days after transplant. An uncomplicated case of vaccine-associated rubella illness was seen after vaccination. Assessment of potential risks and benefits of MMR vaccination given within 2 years of HCT remains important.

Measles outbreak amidst COVID-19 pandemic in Africa: grappling with looming crises

Coronavirus disease 2019 (COVID-19) and measles are major threats to the health and wellbeing of Africans. Measles is an endemic disease in Africa with a high mortality rate especially in children despite available vaccines. This letter aims to discuss the impact of the COVID-19 pandemic on prevention and management of measles in Africa. The emergence of COVID-19 has exacerbated the morbidities of measles due to multi-factors like the disruption of mass measles routine vaccination, a monopolistic focus on COVID-19 eradication, malnutrition, and poor surveillance. Currently, the COVID-19 pandemic and looming measles epidemic pose a double burden on the African health sector. We recommend urgent interventions from government and other stakeholders including community leaders to strengthen measles research and vaccination programs in Africa amidst the pandemic.

100. Safety Analysis of Live-Attenuated Measles, Mumps, Rubella Vaccine Among Hematopoietic Cell Transplant Recipients Vaccinated Within Two Years of Transplant

Background Measles, mumps and rubella (MMR) vaccine is a live-attenuated vaccine usually contraindicated within the first two years of hematopoietic cell transplant (HCT). During the 2019 measles outbreak at our center, the benefits of administering MMR vaccine within the first two years after HCT were weighed against the potential risks. Methods We conducted a retrospective review of patients who received MMR vaccination within two years of an autologous or allogeneic HCT. Patients’ demographics, date and type of HCT, underlying hematologic disease, type of immunosuppressive therapy and date of MMR vaccination were extracted from the electronic medical record. Adverse reactions that could be related to the vaccine were collected for up to 42 days post-vaccination and all hospitalizations and deaths following vaccination were reviewed. Results A total of 129 patients (75 autologous and 54 allogeneic HCT) were vaccinated between 300-729 days after HCT (median of 718 days). The median age at vaccination was 61 years old, 57% of the patients were male and 43% were on immunosuppressive therapy, 87% of whom were on maintenance therapy for multiple myeloma after auto-HCT. Seven patients (5%) had adverse reactions within 42 days of vaccination: six had respiratory tract infections (three with associated fever) and one had a rash leading to a brief hospitalization. This was a 37-year-old female who had an allogeneic HCT 542 days prior to MMR vaccination. She presented with a centrifugal maculopapular rash that was confirmed to be caused by the vaccine strain rubella virus (Fig 1). She fully recovered without sequalae. There was no other vaccine-associated illness identified in the cohort, after a median follow-up of 676 days. Conclusion MMR vaccine appears to be well tolerated in selected HCT recipients when given earlier than 2 years after transplant. No attributable severe outcomes or deaths were described. A mild uncomplicated case of vaccine-associated rubella illness was seen after vaccination. In the setting of a measles outbreak, assessment of potential risks and benefits of MMR vaccination given within two years of HCT remains important. Disclosures Stephen R. Walsh, MDCM, Janssen Vaccines (Scientific Research Study Investigator)Regeneron (Scientific Research Study Investigator)Sanofi Pasteur (Scientific Research Study Investigator) Matthew Cheng, MD, GEn1E Lifesciences (Advisor or Review Panel member)Kanvas Biosciences (Board Member, Shareholder)nplex biosciences (Advisor or Review Panel member) Sanjat Kanjilal, MD, MPH, GlaskoSmithKline (Advisor or Review Panel member) Nicolas C. Issa, MD, AiCuris (Scientific Research Study Investigator)Astellas (Scientific Research Study Investigator)GSK (Scientific Research Study Investigator)Merck (Scientific Research Study Investigator)

The risk factors of measles outbreak in Dollo zone Somali region, Ethiopia

Background: Measles is a highly contagious acute viral illness with the possibility of severe and dangerous complications. Measles occurrence is related to urbanization because of high entry of migrants and high population density; cities have become important hubs for the spread of infectious diseases. The African region is a crucial player in the global fight against measles and has made tremendous progress in its effort to immunize children and to control the disease. Despite the accessibility of safe and cost-effective vaccine, measles has remained endemic with persistent periodic outbreaks in the horn of Africa.Methods: We reviewed the measles cases line lists in Dollo zone from January 2017 to March 2018. There was a total of 771-line listed cases in 2017 and 326 line-listed in 2018. Measles case investigations on alerts were also reviewed when there is an alert rumors verification case investigation done. The line list included variables on vaccination status, age, sex, treatment modality, date of onset the rash, date seen health facility, diagnosis, outcome (alive or dead), locations from place cases came from, contact history and travel history were reviewed.Results: We found that the measles outbreak affected different age groups in Dollo zone and most affected age group were between the ages of 15 years to 30 years and most of the cases have no history of immunization.Conclusions: The outbreak affected all age groups, which may show the continuous low routine immunization coverage over several years and the gathering of the susceptible population in the older age group that may have led to the current outbreak.