Measles

The current outbreak and the vaccine by Dr Sarah Borwein.


Measles is a disease caused by Rubeola virus. It is spread by airborne droplets; making it one of the most contagious diseases known. The average person with measles will infect around 15 other people, and if you are not immune, just being in the same room can be sufficient. People can also spread measles for several days before they even become sick. Because of this extremely high degree of contagiousness, very high levels of herd immunity are required to prevent outbreaks; it's thought that we need more than 95 per cent of the population to be immune to shut down the spread. This requires two doses of vaccine.

The symptoms of measles generally appear about seven-14 days after a person is infected. Typically, measles starts with high fever, cough, runny nose and red watery eyes. Tiny white spots (Koplik spots) can then appear inside the mouth. Three to five days after symptom onset, a rash breaks out. It usually starts on the face at the hairline and spreads down the body. The spots may become joined together as they spread, making the whole body appear red. Fever may spike to more than 40°c.


Some people think of measles as just a little rash and fever that clears up in a few days, but measles can cause serious complications, especially in children younger than five years of age. About one in four people who contract measles require hospitalisation. One in 1,000 develop encephalitis, or swelling of the brain and one or two in 1000 will die, even with the best of care. Luckily, measles does NOT appear to cause birth defects in the baby if contracted during pregnancy.


The best way to protect yourself and your children from measles is vaccination. It is important to vaccinate your children on time and not to delay the vaccine.

The current outbreaks of measles in developed countries are thought to have occurred because too many children have had their vaccines declined, delayed or missed, so that herd immunity levels have fallen far too low.


Whenever there is an outbreak of any vaccine-preventable disease, the sudden surge in demand for the vaccine can make stock levels unstable. In other words, going forward, it's best not to wait for an outbreak in order to vaccinate.

The MMR (measles, mumps and rubella) vaccine is usually given at 12 months of age. At this stage a little over 90 per cent of children seroconvert - or become immune - to measles. The reason the vaccine is not given earlier is because infants whose mothers are immune to measles have passed antibodies to them during pregnancy, and these antibodies can block response to the vaccine, although unfortunately they do not necessarily protect the infant against measles disease. These antibodies wear off at a variable rate - they are mostly gone by 12 months of age, but virtually always by 18 months. It's also important to provide children with protection against measles as soon as possible, and so 12 months is chosen for the first dose because most, although not all, children will be able to respond to the vaccine at this age.


In order to obtain 99 per cent population immunity, a booster dose is required. This second dose is given to children in primary school in Hong Kong, between ages four and six.

Due to the current outbreak, the Hong Kong government is considering advancing the booster shot and giving it earlier, at age 18 months. Other countries, such as Australia and Canada have been implementing similar policies. However, this is currently only a proposal put forward by the Scientific Committee on Vaccine Preventable Diseases, and has not yet been implemented in Hong Kong.


Therefore, at this stage, children are not able to obtain the MMR vaccine early in the public sector.


Stock levels of the MMR vaccine are also very low in the private sector, so you may find surgeries prioritising patients who have not yet received their first vaccine. Contact the local Maternal Child Health Centre if you feel you have an urgent case for being vaccinated. www.fhs.gov.hk/english/centre_det/maternal/maternal.html

If you are an adult and you are unsure about your immunity, a blood test can be carried out with results taking about five business days. The test will help determine whether you need two doses of the vaccine or just one dose or none at all.


Written by Dr Sarah Borwein of Central Health Medical Practice.

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