According to Public Health England (PHE) (2019), influenza is an acute viral infection of the respiratory tract. There are three types of influenza virus: A, B and C. Influenza A and influenza B are responsible for most clinical illnesses. Influenza is highly infectious with a usual incubation period of 1–3 days.
For most healthy people, influenza is an unpleasant but self-limiting illness, although it is far worse than the common cold. Its common symptoms include:
However, it has the potential to cause serious disease that could lead to hospitalisation and accounts for over 8000 deaths in the UK annually.
How does COVID-19 differ from flu?
Common symptoms of COVID-19 include: fever, a new and continuous cough, shortness of breath, fatigue, loss of appetite, anosmia (loss of smell) and ageusia (loss of taste).
The current case community case definition of COVID-19 according to PHE (2020a) is the presence of one of the following symptoms:
Furthermore, the incubation period for COVID-19 is longer than it is for influenza. The time between exposure to the SARS-2-nCoV viruses (being infected) and symptoms onset for COVID-19 is, on average, 5–6 days, but can be up to 14 days (World Health Organization (WHO), 2020a).
Compared with influenza, COVID-19 is more likely to cause serious diseases. The Novel Coronavirus Pneumonia Emergency Response Epidemiology Team (2020) estimated that approximately 15% of patients with COVID-19 will develop severe disease that requires oxygen support, and 5% will have critical disease with complications such as respiratory failure, acute respiratory distress syndrome (ARDS), sepsis and septic shock, thromboembolism, and/or multiorgan failure, including acute kidney injury and cardiac injury. PHE (2020b) reported over 46 000 deaths related to COVID-19 in the UK since January 2020.
Finally, the groups of people who are vulnerable to COVID-19 and influenza are similar, and include those who have long-term/chronic diseases, those who are immunosuppressed, and women who are pregnant (NHS, 2020). There are indications of increased risk of serious disease and death from COVID-19 infection in black and minority ethnic groups (PHE, 2020c); however, the reasons behind this are complex and require further investigation.
How do flu and COVID-19 spread?
Influenza is a highly transmissible viral infection spread by respiratory droplets and direct contact with respiratory secretions. Yan et al (2018) reported that up to 50% of people with confirmed influenza symptoms are sub-clinical but can still spread flu to others.
COVID-19 is thought to mainly transmit through respiratory droplets generated by coughing and sneezing and through contact with contaminated surfaces. During aerosol-generating procedures (AGPs), there is an increased risk of aerosol spread of the infectious agent. Initial research into COVID-19 has identified the virus in stools and conjunctival secretions from confirmed cases; as such, all secretions and excretions, with the exception of sweat, should be considered as potentially infectious (PHE, 2020d).
Social distancing and the use of personal protective equipment (PPE) are the cornerstones of the Government's advice to avoid the spread of COVID-19 (Cabinet Office, 2020). Social distancing should be applied in all places (including within the healthcare environment). If it is impossible to maintain a 2 metre distance, PPE should be used in line with the risks of transmission, for both COVID-19 and flu. The level of PPE required would depend on whether or not AGPs are being performed (Tang et al, 2020). Wearing a higher level of PPE than what is indicated by the risk assessment is not without risks to the wearer and should not be automatically considered as a safer option.
How the flu vaccine is made
The seasonal flu vaccine is designed to protect against three or four of influenza viruses. WHO organises consultation with the Directors of the WHO Collaborating Centres to review the results of the surveillance, laboratory and clinical studies and the availability of vaccine viruses, and then make recommendations on the composition of the influenza vaccine. This year, the WHO (2020b) vaccine recommendation for Northern Hemisphere's vaccine for 2020–2021 are:
The quadrivalent vaccinations both contain inactivated influenza viruses and cause antibodies to develop in the body about 2 weeks after vaccination without causing actual influenza infection. These antibodies provide protection against infection with the viruses (four strains of virus) that are in the vaccine.
Why should I be vaccinated?
PHE (2020e) reported that 70.2% of frontline ambulance clinicians in the NHS ambulance trusts in England were vaccinated against seasonal flu compared with 75.4% of healthcare workers with direct patient contact in acute trusts in 2019–2020. This is an increase of 4.7% across NHS ambulance trusts since the previous year.
It is well known that frontline healthcare workers are more likely to be exposed to the influenza virus and it has been estimated that up to one in four healthcare workers will become infected with influenza during a mild influenza season—this is considerably higher than what is expected within the general population (5.44 cases/100 population per season (Kuster et al, 2011)).
By protecting themselves with the flu vaccine, health and social care workers reduce the risk of spreading flu to patients and of disruption to their care services, which is particularly important throughout winter, when pressures on frontline services may be severe. There is no such thing as natural immunity against the flu virus and staff are encouraged to have their vaccine annually to ensure they are protected. The flu vaccine also reduces the risk of healthcare workers transmitting flu to their families.
The flu vaccine is also offered to the following groups from either their general practitioner or their local pharmacy. As part of making every contact count, we should be encouraging the people in these groups to be vaccinated:
COVID-19 vaccination
At the time of writing, the COVID-19 vaccine is still in development and no product is licenced for use. However, work is ongoing to eventually deliver a COVID-19 vaccine which is safe and effective. Preliminary advice issued by the Joint Committee on Vaccination and Immunisation (Department of Health and Social Care, 2020) has indicated that the priority for vaccination will be frontline health and social care workers and then those at increased risk of serious disease or death from COVID-19 infection. Healthcare workers are at increased personal risk of exposure to the infection and of transmitting that infection to susceptible and vulnerable patients. Vaccination of key workers will protect at-risk populations and help maintain resilience in the NHS.
It is unlikely that the COVID-19 vaccination will be administered at the same time as the flu vaccine and, as such, it is more important than ever that staff are vaccinated as early in the flu campaign as possible to enable them to receive the COVID-19 vaccine when it becomes available.
Conclusion
In conclusion, WHO cites vaccination as the most effective public health intervention in the world, after clean water (Remy et al, 2015). The flu vaccine is considered to be the best protection against an unpredictable virus and has a good safety record, so staff should be vaccinated to protect themselves, their patients and their families. This year, it is important for staff to be vaccinated as early in the flu campaign as possible to ensure that they are able to receive the COVID-19 vaccination should it become available.