World health organization regional office for the western pacific regional guidelines

Delivering an immunization campaign to stop the rubella outbreak

In the face of a rubella epidemic, there will be strong demand to respond with an immunization campaign. For many countries, the priority will be to first strengthen the routine programme and deliver a planned campaign after the outbreak to prevent future cases.

For countries that are already reaching high routine coverage, the addition of rubella vaccine should be considered before any outbreak. Even for countries that have high routine coverage, an immunization campaign to stop the outbreak should only be considered if:

1. 
   Political commitment and additional funding for routine rubella immunization
   
2. 
   Ability to deliver the immunization campaign rapidly and at very high coverage
   

An immunization campaign can potentially interrupt rubella transmission – if rapidly and effectively implemented (high coverage). It needs to be borne in mind that in addition to the time required to plan and implement a campaign, because of the incubation period of the disease it will take a further 2-3 weeks before any reduction in numbers will be seen. However, as previously pointed out an immunization campaign will be far more effective if delivered before an outbreak than during it.

Because of the potential long term risks of poorly or irregularly implemented rubella immunization it is vital to obtain political commitment and funding for routine rubella immunization before considering a campaign.

Effective implementation

There are several key requirements to enable rapid and effective implementation, including:

• 
  Political support for the rubella immunization programme
  
• 
  Availability of funding
  
• 
  Sourcing the vaccine
  
• 
  Sufficient cold chain capacity for the additional load
  
• 
  Sufficient health staff to immunize
  
• 
  Social mobilisation to ensure high uptake (including intersectoral coordination)
  

All these elements need to be in place and coordinated by a national taskforce and secretariat for effective implementation. Effective implementation usually requires careful monitoring and evaluation to identify those who are being missed so that special efforts can be made to reach them.

Options for campaign target groups

Primary school children and pre-school children should always be included in the target group, as they are likely to have the highest attack rates and to be most important groups in spreading the virus in the community. Age-susceptibility profile and age-specific attack rates can help to define which other age groups should also be targeted.

At present WHO does not recommend immunizing pregnant women because of the small theoretical risk of CRS from the vaccine virus. No actual risk has ever been found. During an outbreak, the risk (of CRS) to pregnant women is likely to be greater than the theoretical risk from the vaccine. However, if a vaccinated woman gets infected before she is protected by the immunization, the laboratory test will no longer be able to determine that she has been infected (and thus offered termination) and any subsequent problems in the unborn child will lead to false blame for the vaccine. Therefore, the primary way to protect CBAW is through preventing virus circulating in the community.

If young adults (aged 15-24) have high attack rates, they should be considered for inclusion. However, young adults can be very difficult to target, and it may be possible to focus on adults who are attending institutions or who are in large work places. Although young adults do transmit infection to each other, it is more often infection from school-aged children that drives the outbreak.

It is also possible to protect all childbearing age women (CBAW), not so much because of the impact on the outbreak, but for their future protection. However, an immunization campaign for this wide age-range group should generally happen after all the children have been immunized, and does not have much impact in stopping the outbreak compared to its huge logistic demands.

The logistic challenges of delivering an effective campaign multiply as the target groups increase. Therefore, it is important to plan for initial coverage among the groups where high coverage can be most easily assured (e.g., school-children). It is possible to protect other groups later on, so as to ensure the highest possible coverage in the priority groups who are likely to be the main transmitters of infection in the community. This will usually be school children.

Again, it must be emphasised that a campaign will be much more effective if planned ahead of any outbreak.

References

Acknowledgement

This document was prepared by the Expanded Programme on Immunization Unit and
Osman Mansoor, with helpful comments from Margaret Burgess, Steve Cochi, Richard Duncan, David Featherstone, Susan Reef, Susan Robertson, Alan Ruben, Peter Strebel, Nikki Turner,
Amra Uzicanin.

Annex 1: Rubella infection

The virus

Rubella is single-stranded RNA virus (family: togaviridae; genus: rubivirus) spread by the respiratory route. It only infects humans, leading to the potential for eradication.

The incubation period is 12 to 23 days (usually 16-18) preceding rash. The infectious period is from seven days before to seven days after the onset of the rash; but the virus can be found in the nasopharynnx for up to two weeks after rash onset and babies infected in the womb can shed virus for a year or more.

The illness

Rubella is a common viral infection of childhood that can affect adults. It is usually a mild illness, and often infection does not cause any symptoms. Clinical features include a transient erythematous rash, lymphadenopathy (particularly in the posterior auricular and suboccipital nodes), and, in adults, arthritis or arthralgia.

Rubella may present as a more severe illness, clinically indistinguishable from measles. Rubella encephalitis may occur more frequently than the previously estimated 1 in 6,000 cases. It can result in residual neurological damage or occasionally death, but more often has a benign outcome. Thrombocytopaenia has been reported at a rate of one per 3,000.

Congenital Rubella Syndrome

Rubella infection in early pregnancy can lead to fetal death or Congenital Rubella Syndrome (CRS). The risk of fetal damage depends on timing of the infection: up to 90% at 8 to 10 weeks, declining to about 10% to 20% by about 16 weeks and after this stage of pregnancy, fetal abnormalities are rare.

CRS can cause a wide range of congenital defects (singly or in combination), with hearing impairments the most common. It also causes eye (e.g. cataracts, microphthalmia, glaucoma, pigmentary retinopathy), heart (e.g. patent ductus arteriosus, peripheral pulmonary artery stenosis, or ventricular septal defects), face (e.g. microcephaly) and other defects (encephalitis, mental retardation, autistic behaviour, intrauterine growth retardation, hepatosplenomegaly, interstitial pneumonitis, thrombocytopenic purpura, diabetes, hypothroidism).

In CRS cases the presence of rubella-specific IgM declines with age: ~100% at 0-5 months, ~60% at 6-11 months and rarely after the age of 18 months (although occasionally it may be absent in the fist month after birth)

Epidemiology

Before the use of vaccines, countries usually experienced epidemics every five to nine years, with the highest attack rates in five to nine year old children. Rubella also circulates in between epidemics. Rubella is not as infectious as measles and many adults remain susceptible to rubella.

Immunization can eliminate rubella. In countries with selective immunization of girls/women, outbreaks have occurred that predominantly affect adult males.

Laboratory diagnosis

Diagnosis cannot be reliably be made on clinical grounds and laboratory testing is needed to confirm the diagnosis. The standard test is rubella-specific IgM test (positive from 6 days to 6 weeks after rash onset) [**note WHO99 states 4 days to 4-12 weeks**].

Diagnosis can also be made from an increase in rubella-specific IgG in paired serum, viral isolation, or PCR. Virus can be isolated from nasal, blood, throat, urine, stool or cerebrospinal fluid samples. Samples are best taken within four days of rash onset when the viral load is highest. The best results come from throat swabs. Isolates or PCR results can be used for genotyping the virus that may help determines the source.