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Key Clinical Updates in Major Vaccine-Preventable Viral Infections

A novel oral polio vaccine type 2 (nOPV2) has been developed in response to the ongoing circulating vaccine-derived type 2 poliovirus outbreaks and has been shown to be safe and immunogenic in previously immunized adults. Studies have shown that nOPV2 is more genetically stable than the mOPV2 and therefore less prone to reverting to neurovirulence. The nOPV2 was recommended for initial use under the World Health Organization’s Emergency Use Listing Procedure in November 2020.

Coster ID et al. Lancet. [PMID: 33308429]



  • Onset of prodrome 7–18 days after exposure in an unvaccinated patient.

  • Prodrome: fever, coryza, cough, conjunctivitis, malaise, irritability, photophobia, Koplik spots.

  • Rash: brick red, maculopapular; appears 3–4 days after onset of prodrome; begins on the face and proceeds “downward and outward,” affecting the palms and soles last.

  • Leukopenia.

General Considerations

Measles is a reportable acute systemic paramyxoviral infection transmitted by direct contact with infectious droplets or by airborne spread. It is highly contagious with communicability greatest during the pre-eruptive and catarrhal stages but continues 4 days after the appearance of rash. Measles elimination is defined as the absence of endemic measles virus transmission in an area for 12 months or longer. Measles remains a major cause of mortality with more than 140,000 estimated deaths globally in 2018, mostly in children younger than 5 years old.

In 2020, there was more than an 80% decrease in reported measles cases. This is likely due to the deterioration of existing surveillance, testing, and reporting of measles. The World Health Organization (WHO) previously considered measles eradicated in most countries worldwide, including the Americas. Many countries, however, are reporting ongoing measles outbreaks, including the Democratic Republic of the Congo, Nigeria, Pakistan, Somalia, Afghanistan, Burkina Faso, Côte d’Ivoire, Ethiopia, Niger, and India. During 2019, measles outbreaks occurred in countries with high vaccination coverage, including the United States, Israel, Thailand, Tunisia, New Zealand, and many European countries and the Pacific Islands. For 2020, the WHO European Region reported a total of 12,205 measles cases; this is compared to 104,554 cases and 42 deaths in 2019.

Most measles cases in the United States are due to either travel to endemic areas or exposure to individuals who have not been vaccinated against measles. Between January 1 and November 3, 2021, a total of 47 measles cases were reported in four states of the United States. Nearly 1300 cases of measles were reported in 2019, the most cases reported in a single year since 1992. Included in this number are two large outbreaks in New York Orthodox Jewish communities, which accounted for 934 (75%) cases during 2019. Previously, the highest number of reported measles cases was 667 in 27 states in 2014 followed by 372 in 2018. Intentional undervaccination continues to undermine measles elimination programs, and many measles vaccination ...

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