Measles, Mumps, Rubella and Varicella (Chicken Pox) are highly contagious viral diseases that can affect both children and adult without immunity.

These diseases can spread through air droplets or direct contact with respiratory secretions of infected persons. Infants and immunocompromised patients are at risk of developing severe disease and complications from such the infection.

Symptoms of Measles appear 7 to 21 days after exposure and patients can present with fever, runny nose, cough, red eyes, skin rash and whitish lesions in the mouth. Severe cases can lead to pneumonia, encephalitis (infection of brain) and even death.

Mumps usually present at 12 to 25 days of exposure. It causes fever, swelling and inflammation of the salivary glands (parotid glands) and occasionally affects the brain (meningoencephalitis) and testes or ovaries (Orchitis or Oophoritis).

Rubella is also known as German Measles. It presents as fever and skin rash. It may affect pregnant women and their foetus causing still birth and congenital abnormalities including hearing loss, cataract, cardiac disease and neurodevelopmental defects.

Varicella, also known as Chicken Pox, presents with fever, vesicular skin lesions, occasionally pneumonia and brain infection (encephalitis) after 10 to 21 days of exposure. After the primary infection, some patients may develop herpes zoster at later life.

Currently, there are effective vaccines to prevent the above infections. Both MMR and Chicken Pox vaccines are live attenuated vaccines and they are included in childhood immunization programs in Hong Kong.

The 1st dose of MMR and Chicken Pox vaccines are given at one year old at two different injection sites (to decrease risk of febrile convulsion as opposed to the combined MMRV vaccine). The 2nd dose combined MMRV vaccine is given at 18 months old. The effectiveness of 2 doses of MMR and Varicella vaccines are 97% and 95% respectively.

Common side effects of the MMR vaccine include fever, local site reactions and skin rashes. Uncommon side effects include low platelet count, allergic reactions and febrile convulsions.

Common side effects of the Varicella vaccine include fever, local site reactions and skin rash. Uncommon side effects include allergic reactions.