Flu vaccination in the times of Covid-19

The prospect of a flu season during the coronavirus pandemic is frightening to health experts.

What disease are you most concerned about catching this autumn? Probably not the flu! More likely, Covid-19 is the worry on your mind. But the flu season is coming soon.

In the northern and southern hemispheres, influenza outbreaks occur mainly in the respective winter seasons. Influenza spreads globally, annually, with significant paediatric and adult attack rates and considerable morbidity, mortality and the exacerbation of existent chronic disease. Around 20% of unvaccinated children and 10% of unvaccinated adults are infected annually.

This winter, in the absence of a vaccine, the novel coronavirus Covid-19 will also circulate in parallel with seasonal influenza. Several strains of influenza and of Covid-19 will circulate, including strains still to come. Influenza vaccination, although available, is only partially effective. It would be advisable to attempt near universal population coverage with the annual influenza vaccine leading up to next winter to obtain herd immunity or approach it.

So far it appears that, with the current strains of these two viruses, the clinical outcome of co-infection is not significantly worse than infection with Covid-19 by itself.

Flu virus high mutation
Due to the high mutation rate of the influenza virus, the World Health Organisation predicts each year which influenza strains are likeliest to circulate in the next year, making it possible for pharmaceutical companies to produce targeted vaccines. As predictions are not infallible, the vaccine will not include all the active strains in any particular season, and it is occasionally possible for a new or overlooked and therefore non-included strain to become prevalent and widespread. The vaccine induces immunity in about two weeks after administration. It is worth noting that this vaccine can precipitate reactions similar to true infection, but not as severe or long-lasting as actual disease.

Seasonal influenza vaccination is absolutely cost-effective, especially in children and the elderly.

Universal influenza vaccination is also relevant to alleviate hospitals and other health systems from the significant pressure of dealing with both Covid and influenza complications at the same time.

A bigger challenge
This year humanity will be facing a bigger challenge, a unique influenza year, as seasonal influenza that is still not fully preventable is going to be confounded by the Covid-19 pandemic. We still do not have full understanding of the immune response to these viruses and we must not forget that bacterial superinfection is one of the deadliest complications of influenza. The upcoming flu season will be a challenge not to miss sequential or mixed infections with influenza and SARS-CoV-2.

Children are susceptible to both, may be co-infected and are also well known to play an important role in transmission of influenza and the pneumococcus to the elderly. Traditional inactivated influenza vaccines in the elderly are less effective, due to diminished immunity response, thus, in the current Covid-19 era, direct protection of the elderly through pneumococcal vaccination is equally important.

Patients with moderate to severe asthma should all receive influenza vaccination because of the possibility of concurrent Covid infections. Influenza vaccination can reduce the number of serious illnesses, such as lower respiratory tract infections requiring hospitalisation and death in COPD patients. These patients are urged to protect themselves with influenza vaccine, in particular due to increased risk of Covid-19 infection.

Flu vaccine and heart disease? 
The risk of having a heart attack is six times higher in the week after a bout of the flu. Viruses like influenza, ‘the flu’, can cause an inflammatory response in the body, placing strain on the heart; this could lead to heart failure or an abnormal heartbeat. The flu can also destabilise plaque in your blood vessels, and this can cause a blockage and possible heart attack.

The flu vaccine does not protect against Covid-19, but it does help to prevent the flu and protect the heart. 

Covid-19 (SARS-CoV-2) is currently a global pandemic
Influenza spreads annually with significant morbidity and mortality
Next winter both viruses will circulate and co-infect hosts
Influenza vaccination is available but not completely effective

It is clear that the universal uptake of the influenza vaccine would be ideal this winter, and there are no doubts that an almost universal uptake may engender herd immunity and help to protect those in who the vaccine is ineffective.

By any rational viewpoint, convincing people to get a flu vaccine should not be a challenge but indeed it is! People hoping for a vaccine against Covid-19 may find it hard to rationalise why they are not taking advantage of a flu vaccine that is already available. Covid-19 is not the flu, but they are similar, they both are respiratory diseases with considerable lethality, particularly among vulnerable populations. 

The sooner you can get a flu vaccine, the less of a chance you will have of getting seriously ill during the autumn and winter months.

To avoid a complex situation and a possible double infection, do not miss the influenza vaccine this year. And the pneumococcal vaccine is also important.

Protect yourself and others around you.

Getting a flu vaccine now will help in the global fight against COVID-19.

Best health wishes,
Maria Alice

|| features@algarveresident.com
Dr Maria Alice is a consultant in General and Family Medicine. General Manager/Medical Director – Luzdoc International Medical Service. Medical Director – Grupo Hospital Particular do Algarve/ Hospital S. Gonçalo de Lagos