Open Access
Immunisation update

Keeping up with vaccinations. What's new, what's available and who to ask for help

ARCHANA KOIRALA, LUCY DENG, Nicholas Wood
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Two doses of the MMR vaccine for all

To prevent measles outbreaks, it is essential that all eligible individuals living in Australia are immune to measles. Before 1966, the measles virus was circulating in the community and individuals born before that year are likely to have a natural immunity to measles.31 People who were born between 1966 and 1994 may have received only a single dose of a measles-containing vaccine and, therefore, a proportion may not be immune to measles.32 

One dose of measles-containing vaccine is 95 to 96% effective. Effectiveness increases to 99% after a second dose.33,34 It is therefore recommended that all eligible individuals born after 1966 who are living in or visiting Australia receive two doses of a measles-containing vaccine. This requires that some patients receive catch-up vaccinations.4 A flow chart (Figure 2) has been created by NCIRS to aid GPs in advising patients on catch-up vaccinations.35 When it is uncertain whether a person has natural immunity or has received two doses of measles-containing vaccine, an additional MMR vaccine should be administered. There is no known increase in adverse events from vaccinating people with pre-existing immunity to measles.4

Routine serological testing for measles IgG to assess immunity from either natural infection or vaccination is not recommended in lieu of vaccination, but may be an alternative way to confirm measles immunity, particularly in populations where the MMR vaccine is contraindicated.4,35 Sensitivity of the test varies by assay and time since vaccination.36-38 

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Pregnancy and vaccination

Vaccination needs should be assessed for women planning pregnancy and those who are pregnant. It is important that GPs discuss immunisation with women planning pregnancy and ensure that they are up-to-date on their immunisation schedules, particularly against rubella and chicken pox. These live vaccines can harm the fetus if contracted during pregnancy and should be given before pregnancy not during. Influenza and diphtheria-tetanus-acellular pertussis (dTpa) vaccines are recommended for pregnant women and are funded by the NIP.

Whooping cough vaccination in pregnancy

The pertussis vaccine (dTpa) is an inactivated vaccine provided free for pregnant women under the NIP, and recommended to be given in each pregnancy (even pregnancies that are closely spaced). Vaccination in pregnancy allows for maternal antibody production and in utero transfer to the fetus, protecting up to 90% of infants until the age of 3 months against hospitalisation from pertussis when the mother is vaccinated at least seven days before delivery.39-41 The vaccine also protects pregnant women from contracting pertussis and reduces the likelihood of it spreading to other adults and their children. The recommended timing of the pertussis vaccination in pregnancy has expanded from between 28 and 32 weeks to between 20 and 32 weeks. This allows greater opportunities for health services to offer vaccination to pregnant women, to protect premature infants and to improve vaccine coverage.4

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If the vaccine has not been given by 32 weeks of pregnancy it can still be given at any time during the third trimester. Additionally, if a pregnant woman receives the vaccine earlier than 20 weeks, she does not need a repeat dose during the same pregnancy. Evidence shows transfer of pertussis antibodies to the infant in women who received dTpa vaccine as early as 13 weeks’ gestation.42 

The vaccine is safe and well tolerated in pregnancy. Safety studies suggest that vaccination in the second and third trimester is not associated with clinically significant harm to the fetus or the mother.42 Active surveillance of 5085 pregnant Australian women between 1 July 2018 and 30 June 2019 showed 94% had no adverse effects following dTpa vaccination. The most common adverse event was injection site pain (2.4%), followed by injection site swelling or erythema (1.7%). Fever occurred in 0.8% of women and only 0.5% of women required any medical attendance.43 The only absolute contra-indication to dTpa in pregnancy is a history of anaphylaxis to the vaccine.4

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Influenza vaccination in pregnancy

Influenza in pregnant women and children less than 6 months of age is related to increased disease severity and risk of complications such as premature delivery and neonatal or perinatal death.44-47 Vaccination during pregnancy ensures protection for both the mother and her infant up to 6 months of age, after which children are eligible to receive their own vaccine.48-52 The seasonal influenza vaccine has been shown to decrease influenza cases in pregnant women by 50% and hospitalisation by 35 to 40%.46,51,53,54 Infants less than 6 months of age were half as likely to develop influenza and 72% less likely to require hospitalisations when their mother received the influenza vaccine in pregnancy.48 The seasonal influenza vaccine is safe throughout all trimesters of pregnancy and only one dose is recommended each season.4,50,55 Pregnant women are advised to receive a second dose of the influenza vaccine if their first dose was the previous year’s seasonal influenza vaccine.12

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Dr Koirala is an Immunisation Fellow at the National Centre for Immunisation Research and Surveillance (NCIRS), Sydney; Paediatric Infectious Diseases Specialist at Nepean Hospital, Kingswood; and Clinical Associate Lecturer at The University of Sydney Children’s Hospital Westmead Clinical School, Sydney. Dr Deng is a Staff Specialist at NCIRS, Sydney; Paediatrician at The Children’s Hospital at Westmead, Sydney; and Clinical Associate Lecturer at The University of Sydney Children’s Hospital Westmead Clinical School, Sydney. Dr Wood is a Senior Staff Specialist at NCIRS, Sydney; Paediatrician at The Children’s Hospital at Westmead, Sydney; and Associate Professor at The University of Sydney Children’s Hospital Westmead Clinical School, Sydney, NSW.