Influenza vaccination for people with egg allergy
Influenza vaccines in Australia are grown in embryonated chicken eggs and historically there have been concerns regarding the risk of anaphylaxis following influenza vaccination in people with egg allergy. However, manufacturing processes ensure that only a trace amount of ovalbumin remains within the vaccine formulation (usually less than 1 mcg of ovalbumin per dose), which is insufficient to cause anaphylaxis.4
In a 2014 review of 28 studies encompassing 4315 people with egg allergy (including 656 people with a history of anaphylaxis), no severe reactions were reported after influenza vaccination.13 Vaccine allergy testing, split dosing or graded administration are no longer recommended when vaccinating people with egg allergy as they have shown no difference in the rate of adverse reactions.14 People with egg allergy do not need to be referred to specialist hospital-based vaccination clinics for influenza vaccination; however, anyone administering a vaccine should have training and equipment for the rapid recognition and treatment of anaphylaxis.4 The Australasian Society of Clinical Immunology and Allergy has developed guidelines on vaccinating egg – allergic people (www.allergy.org.au/hp/papers/vaccination-of-the-egg-allergic-individual).14
Influenza and Guillain-Barré syndrome
Guillain-Barré syndrome (GBS) is a rare, acute immune-mediated polyneuropathy, commonly preceded and thought to be triggered by gastrointestinal or respiratory infections, including influenza. Concerns about the association between GBS and influenza vaccination arose after an increased number of cases of GBS were reported following swine flu vaccination in 1976.15 Further studies have shown that GBS is rare after seasonal influenza vaccination, and at most may account for one additional case of GBS per million vaccine doses.15-17
The risk of developing GBS after influenza is 15 times higher than after influenza vaccination. Therefore, in patients with a history of GBS, the benefits of vaccination may outweigh the risk of recurrent GBS after vaccination.18 Reassuringly, no recurrences of GBS were reported in 214 patients with a history of GBS, pooled from three studies, who received a total of 1195 doses of influenza vaccine after their GBS diagnosis.19-21 Another study reported a recurrence of GBS-like symptoms following influenza vaccination in eight out of 211 patients with a history of GBS, but formal diagnosis of a relapse was not confirmed, most symptoms were mild and no patient required treatment or hospitalisation.22 When considering vaccination of a patient with a past history of GBS, GPs should consider the patient’s risk factors for severe influenza illness such as diabetes, any respiratory or cardiac condition, temporal association with the influenza vaccine and the possibility of a reasonable alternative trigger such as Campylobacter gastroenteritis. Vaccination is recommended unless the previous onset of GBS, without a potential alternative trigger, occurred within six weeks (42 days) of receiving the influenza vaccine (Flowchart).
Measles is a highly infectious disease caused by a paramyxovirus and spread by aerosolised or droplet respiratory secretions. Complications of measles include otitis media, diarrhoea, pneumonia and encephalopathy, and measles remains one of the leading causes of death among young children.23 Measles outbreaks have increased globally over the past few years, with the WHO estimating a 300% increase in reported cases in the first three months of 2019 resulting from gaps in vaccine coverage.24
In Australia, children are typically vaccinated against measles from 12 months of age, and therefore most measles cases are imported, occurring in unvaccinated or undervaccinated individuals infected while travelling to endemic or outbreak regions. Due to the constant importation of measles, there is a risk of spread to unvaccinated individuals, in particular children under the age of 1 year, in people who have not received two doses of measles-containing vaccine and immunocompromised individuals who cannot receive live vaccines.25 As a consequence, to improve measles immunity in the community, the Australian Immunisation Handbook has updated its recommendations as follows:
- children as young as 6 months of age can receive the measles, mumps and rubella (MMR) vaccine
- all Australians should receive two doses of the MMR vaccine.
Measles vaccination from age 6 months
The Australian Immunisation Handbook has lowered the recommended age that children can receive the MMR vaccine from age 9 months to 6 months for children travelling to endemic areas, in outbreak situations and for postexposure prophylaxis in line with WHO and Centers for Disease Control and Prevention (CDC) recommendations.4 The change in recommendation comes as a result of increasing evidence suggesting that vaccinated women have an earlier decline in circulating antibodies compared with women who have been infected with measles, resulting in lower titres of maternal antibodies being transferred to the fetus during pregnancy. 26-29 These lower titres result in a shorter period of protection in infants and a longer period of time that they are at risk of measles infection before their first dose of MMR vaccine. Countries that have lowered the recommended age of measles vaccination to as young as 6 months of age, including the US, Canada, UK and New Zealand, have reported no additional safety concerns.30 Vaccinating infants between 6 and 11 months of age provides short-term protective antibody levels in a large proportion of infants and should be considered in addition to the routine two-dose schedule at 12 and 18 months to ensure long-term immunity.24