US measles outbreak: Should you be worried? | CNA Explains

Key Concepts

• Measles: Acute viral disease caused by the measles virus.
• MMR Vaccine: Measles, mumps, and rubella vaccine.
• Respiratory Droplets: Primary mode of measles transmission.
• Immune Suppression: Measles' effect on weakening the immune system.
• Vaccination Rate: Percentage of the population vaccinated against measles.
• Herd Immunity: Protection conferred to unvaccinated individuals by a high vaccination rate in the community.

Measles: An Overview

• Measles is a highly contagious viral disease caused by the measles virus, spread through respiratory droplets (coughing, sneezing).
• It is considered one of the most transmissible viruses globally. One infected person can quickly spread the virus to approximately 15 others in an environment like a school.
• Symptoms include fever and rash, but the primary concern is the immune suppression it causes.

Impact of Measles on the Immune System

• Measles suppresses the immune system, making individuals vulnerable to secondary infections like pneumonia, which can be fatal.
• The virus can erase the immune system's memory, including protection from prior vaccinations, requiring revaccination.
• The immune suppression allows normally controlled bacteria in the body to overgrow, leading to infections.

Measles Outbreak and Vaccination

• Measles outbreaks are directly linked to decreased vaccination rates, falling below the critical threshold of 95%.
• The MMR vaccine is a combined vaccine protecting against measles, mumps, and rubella.
• A 95% vaccination rate is essential to prevent measles outbreaks due to the virus's high transmissibility.
• The decline in vaccination rates is attributed to misinformation, specifically the debunked claim linking the MMR vaccine to autism. The study that initially suggested this link was retracted due to fraudulent data.

Singapore's Measles Situation

• Vaccination is not mandatory in Singapore, but schools require a complete vaccination schedule for enrollment.
• Singapore has a high vaccination rate, with over 90% of the population having received two doses of the MMR vaccine and over 95% having received at least one dose.
• Children in Singapore typically receive the first MMR dose at 12 months and the second at 15 months.
• Measles is rare in Singapore, but there were 10 cases recorded as of mid-May 2025, close to the total of 11 cases in 2024.
• The high vaccination rate prevents outbreaks, but the remaining unvaccinated 5% are still susceptible to infection when exposed to measles.
• Travel from regions with lower vaccination rates increases the risk of imported cases in Singapore.

Conclusion

Measles remains a significant public health concern due to its high transmissibility and potential complications. Maintaining high vaccination rates is crucial to prevent outbreaks and protect vulnerable populations. While Singapore has a high vaccination rate that prevents outbreaks, imported cases remain a risk, highlighting the importance of global vaccination efforts and combating misinformation.