Given the unpredictable nature of flu viruses, should vulnerable patients be revaccinated?
The 2017 flu season could be a turning point in deciding how GPs can help protect patients from influenza.
New flu cases have surged in recent weeks, instead of tapering off as would be expected normally after an early start to the season. Nationally, confirmed cases exceeded 75,000 last week and are expected to surpass 100,000.
Professor Paul VanBuynder, chair of the Immunisation Coalition, said many GPs were questioning whether vulnerable patients needed added protection, given evidence that vaccine efficacy falls off more rapidly in elderly and other at-risk patients.
“I get that question every day from general practitioners. Should we be revaccinating people if the flu season is bad and they are particularly at risk of disease?” Professor VanBuynder said in response to a question from The Medical Republic at a media briefing last week.
“There are no data on revaccination in studies, and there are no expert bodies that recommend revaccination for influenza vaccine,” he said.
“I know some GPs are doing it. Certainly, we don’t have a policy that says please get vaccinated in March and then repeat it in August, but I am open to general practitioners looking at people who are particularly severely at risk.
“The reality is, there’s no harm to that; there’s no increased risk in terms of side-effects. But we don’t recommend it as a general principle. We think healthy people should be protected through the flu season as long as they don’t get (vaccinated) too early.”
International studies indicate influenza vaccine effectiveness dissipates in people with a normal immune response over six months, but the drop-off varies according to age.
The Australian Technical Advisory Group on Immunisation says recent evidence suggests protection begins to decline after three to four months. The group has counselled against early vaccination for that reason.
In Australia, however, two doses of flu vaccine are recommended only for children aged between six months and nine years in their first year of vaccination.
Professor VanBuynder, a public health physician at Gold Coast Health, said refraining from early vaccination was one way of extending protection in the general population.
He actually delayed the vaccine this year in his Queensland jurisdiction, and in Western Australia there was a formal policy of asking patients to refrain from vaccination until May.
But such recommendations had not been adopted outside Australia, he said.
Working against that tactic, however, this year’s flu season arrived three to four weeks early and is shaping up as one of the worst on record, based on sheer numbers of confirmed cases.
In recent weeks, thousands of new notifications in Queensland, NSW, Victoria and South Australia have lifted the 2017 total past 75,000 cases, with the virulent Type A (H3N2) dominating in new presentations, after Type B flu was prominent earlier on.
According to Professor Ian Barr, acting director of the Melbourne-based WHO Collaborating Centre for Research and Reference on Influenza, about 70% of cases this year have been Type A (H3N2), 20% Type B of the Yamagata lineage, and 10% Type A (H1N1).
In this year’s quadrivalent vaccine, the two Type B components and the Type A H1 strain appeared to be reasonably good matches with the viruses affecting the population, he said.
“For the H3, that’s a virus that causes us a lot of headaches, and that virus I’d say is a moderate match to what’s in the vaccine,” Professor Barr told The Medical Republic.
The Type A (H3N2) affects all age groups and is responsible for most flu-related hospitalisations, typically involving patients in the 60 to 80 years age group.
Australia’s vaccine was designed months in advance of the southern flu season based on the previous northern hemisphere virus activity. It could never be an identical match with viruses mutating in the wild, Professor Barr said.
Underlining the unpredictable nature of flu viruses, the character of this year’s attack differs markedly across the country. While Western Australia has been relatively unscathed with fewer than 2000 cases, Queensland expects to break all records. And notifications in South Australia are at a six-year high.
At August 16, NSW had confirmed 35,315 cases, followed by Queensland (19,662), Victoria (8,600) and SA (7,501). So far, other states and territories have got off lightly.
Professor Lou Irving, director of respiratory medicine at Melbourne Health, said 20% of proven flu-related hospital admissions in his jurisdiction were in the under-40 age group and 27% were aged 40 to 65 years.
“Only half of admissions were the age you would expect – over 65,” Professor Irving told the media briefing.
He said there were strong public health reasons for policy changes to add flu vaccines for children to the National Immunisation Program, including their role as “super carriers” of the virus, and to expand coverage for at-risk groups.
Fewer than 10% of Australian children in the 10 to 19 age bracket are vaccinated against flu. Patients aged 5 to 19, incidentally, have accounted for the greater part of the recent spike in Queensland’s flu cases.
Among elderly patients, who are most prone to complications from flu, Australia’s vaccination rate is just 75% to 80%.
But coverage is even worse for other vulnerable groups. Only 50% of pregnant women, and 35% of patients with chronic disease are vaccinated.
Professor Irving emphasised that life-threatening complications from influenza were not confined to the elderly and were underestimated in the community. Parents did not take flu vaccination for children seriously because it was not funded, he said.
He cited the recent case of a 38-year-old Melbourne woman who caught Type A influenza from one of her children shortly before going into labour with her third child. Three days post-delivery, she was admitted to ICU with acute cough, pleuritic chest pain and a diagnosis of pneumococcal pneumonia.
In another case, a man aged 27 was admitted with evidence of pneumonia linked to his daughter who had Type A influenza. He was treated with antivirals and antibiotics but required surgical drainage of pus and fluid from his lungs, and an 11-day stay in hospital.
Professor Robert Booy, head of clinical research at the National Centre for Immunisation Research and Surveillance, said experts understood that vulnerable patients’ immunity would decline over the winter, but they were not at the point of making a public-health recommendation for flu booster shots.
“If we are finding that come August (data), we are getting a lot of at-risk people who no longer have vaccine efficacy, that will have to be seriously considered,” he said.
