Recent rubella outbreaks in Japan and Poland are the clearest evidence possible that herd immunity matters.
There are many reasons why people don’t get vaccinated for totally preventable diseases such as rubella. One major issue is anxieties around safety, such as in the case of the MMR (measles, mumps and rubella) combination vaccine in the UK. Faulty science published 15 years ago suggested a now debunked link between the vaccine and autism. Fear spread and vaccinations plummeted.
In 2013, the recent serious measles outbreak was fuelled by children who weren’t vaccinated a decade ago. The disease primarily affected teenagers but spread to infants who were too young to be vaccinated. There are now also concerns that outbreaks of mumps and rubella - the remaining “M” and “R” in MMR - could follow.
Outbreaks of vaccine preventable diseases can also happen, not because of individual or community refusals to vaccinate, but due to lack of access to a vaccine, because of supply or cost issues for example, or because of policy decisions as to who gets vaccines and who doesn’t.
Japan and Poland - uneven vaccination cover
Japan first introduced the rubella vaccine into its national immunisation programme in 1976 but it was only given to junior secondary school girls. In 1989, Japan introduced the MMR vaccine for all children aged one to six, but that left a 13-year gap where no boys were immunised.
Rubella vaccination is targeted at girls because although it only produces mild symptoms in sufferers, it can be catastrophic for unborn babies. If a pregnant woman catches the disease, it can spread to the fetus, causing miscarriage, stillbirth and congenital rubella syndrome, which can cause various severe birth defects.
But men still catch the disease and in Japan, where rubella cases have shot up to over 10,000 cases, [about 77% of them are in young men](http://www.cdc.gov/mmwr/pdf/wk/mm6223.pdf](http://www.cdc.gov/mmwr/pdf/wk/mm6223.pdf) aged between 20 and 40.
An additional issue with the MMR vaccine led to it being withdrawn in 1993 after an adverse event occurred related to the mumps part of the vaccine. In 2006, an MR (measles and rubella only) vaccine was introduced for children, leaving another coverage gap for both boys and girls for the years between 1993 and 2006. This time the government did a “catch-up” campaign to vaccinate those children who missed their vaccines during the time of the MMR vaccine suspension.
The value of this catch-up campaign is clear when you look at who contracted rubella in Japan’s outbreaks. Those boys who missed the rubella vaccine in the earlier “girls only” policy – now 20-39 year old men – were 68% of those who contracted rubella in the outbreak.
The introduction of the MR vaccine for all children, and the catch-up campaign for those who missed vaccination in the gap between MMR suspension and the introduction of the MR vaccine, paid off. Only 5.6% of the rubella cases were among children aged under 15 years old.
In Poland, since the start of the year to mid-June there were more than 26,000 cases of rubella. Similar to Japan, over 80% of the cases were among males aged between 15 and 29. And again this is the result of a policy decision to target 13-year-old girls when the rubella vaccine was introduced in Poland in 1989.
In 2004, the MMR combination vaccine was offered to both boys and girls in Poland (at 13-15 months old, with a second dose at 10-years-old) making coverage more gender neutral.
Both the Japanese and Polish outbreaks are largely attributable to policy decisions made more than two decades ago.
Most of those who contracted rubella did not refuse, or rather their parents did not refuse, to take the vaccine - they were simply never offered it. Also in both of these outbreaks, the policy decision was to focus on immunising girls, not boys.
And Japan and Poland aren’t the first countries to pay the price of selective rubella vaccination policies. Romania had an outbreak of more than 20,000 rubella cases in 2011-2012 and Greece had large outbreaks in 1993 and 1999, all consequences of earlier vaccine policies.
The health threats posed by these historic decisions also stretch beyond the immediate countries affected.
In order to minimise the risk of importing rubella, as well as protecting individual health, the US Centers for Disease Control (CDC), for instance, recently issued an alert recommending that travellers to Japan or Poland ensure that their rubella vaccinations were up to date. Pregnant women were urged not to travel at all if they were unvaccinated.
While there are sometimes legitimate reasons to focus vaccine policies on those most immediately at risk, especially in times of limited vaccine supply or financial constraints, the value of vaccines depends on achieving a level of “herd immunity”.
In other words, if not enough of the “herd” or larger population get vaccinated, the virus continues to circulate and can infect anyone not vaccinated. And, as we’ve seen in Japan, Poland and elsewhere, the impact of these policies can hit years later.
Vaccination policies and programmes need to be designed to take a long-term view. And we need to stay vigilant to the risks of vaccination gaps before they become a crisis.