Myths and realities about the flu and its vaccine

By José María Bayas Rodríguez, University of Barcelona

"The flu vaccine feels fatal to me." Or "even if I get vaccinated, I get the same cold." Or "I don't get vaccinated anymore because one year I did it and took more flu than ever "Or, also," is that the vaccine produces me flu" They are some of the topics that are heard every winter coinciding with the flu vaccination campaign. Topics in which some health professionals also fall.

In many cases it is due to the usual confusion between flu and cold. And in others, to coincide in time having been vaccinated and getting a cold. Or simply that everything “bad” that happens after receiving any vaccine can be mistakenly imputed to vaccination, confusing consequence with sequence.

But let's start at the beginning: understand what we mean when we talk about the flu. It is an acute viral infection of the upper respiratory tract (nose, throat, trachea and bronchi) and, occasionally, of the lower (lungs). The infection usually evolves within a week and is usually characterized by sudden onset of high fever, muscle aches, headache, malaise, dry cough, sore throat and rhinitis.

Flu vs cold

And what distinguishes it from a common cold or cold? To start that in the cold the onset is progressive. And also that when we are crammed there is usually nasal congestion, abundant nasal secretion and frequent sneezing. But no sign of fever or muscle aches.

Gravity is another important distinction. Most people affected by the flu recover without medical treatment. But young children, the elderly, patients with previous illnesses and pregnant women can suffer major complications, even fatal ones.

With everything and with that, the most normal thing is that the flu comes out safe and sound. What happens is that, as all people suffer several flu infections throughout life, in the end the disease has an important impact on world health.

Thus, WHO has estimated that about 1 billion cases are recorded in the world every year, of which between 3 and 5 million are serious. And the numbers say that between 290,000 and 650,000 people die from respiratory causes related to the flu.

The common cold can be caused by about 200 viruses, mostly rhinoviruses and coronaviruses, while the flu-responsible viruses belong to the family. Orthomyxoviridae. The human flu is caused by the genders Influenzavirus A and B and, sporadically, by Influenzavirus C.

Both are easily transmitted from one person to another through small particles ejected with a cough or sneeze. Especially in agglomeration situations and in cold weather.

In addition, as influenza viruses damage the respiratory epithelium, there may be complications from secondary infections, mainly caused by streptococci and staphylococci.

3D rendering of a flu virus. Naeblys / Shutterstock

Why it is impossible to eradicate the flu

Flu there is not one but several. The most ubiquitous is influenza A, whose main natural reservoir is migratory wild birds. Although it also infects domestic birds (chickens, ducks and turkeys) and numerous species of terrestrial and marine mammals, such as pigs, felines, seals and whales. Without forgetting, of course, of man.

In addition to being ubiquitous, influenza A viruses have several “super powers” ​​that make it difficult for us to face them. On the one hand, its high genetic variability, associated with changes in viral coat proteins. When two strains of different subtypes co-infect the same host, they exchange genetic material that can lead to new viruses. Influenza viruses also have the ability to "jump species", that is, viruses that are typical of birds or pigs get infected and sometimes spread in the human species.

Constant mutations give rise to new viruses that cause seasonal epidemics of influenza A virus and B virus. Therefore, although flu vaccines with high effectiveness and safety to control the flu, must be updated and administered every year. And so also, the eradication of influenza is quite impossible.

American soldier sprays his throat to prevent the flu during the flu pandemic Everett Historical / Shutterstock

The thing is further complicated when the mutations are so large, the virus is so "new" that we go from epidemic to pandemic (global scale epidemic). During the twentieth century, three pandemics per virus were registered, mainly of avian origin: the “Spanish” (1918, subtype A H1N1), the Asian (1957, subtype A H2N2) and that of Hong Kong (1968, subtype A H3N2). The 2009 pandemic had a porcine origin (A H1N1pdm).

The danger is not getting vaccinated

Does it vaccinate yes or no? Clearly, yes. WHO does not hesitate in that: the flu vaccination is the most effective measure to prevent the onset of the disease and limit its spread in the population with the highest risk of complications.

Vaccination reduces respiratory diseases and flu-related deaths. It also reduces medical consultations, hospitalizations and absenteeism.

At a minimum, vaccination is recommended for people at high risk of complications in case of the flu, for those over 60-65 years and pregnant women. And it is unavoidable when we talk about health personnel, who are vaccinated to protect the patients they treat, but also for professionals necessary for society to function (state security forces and bodies and firefighters, among others). Without forgetting the people who live with a population at risk (the "living together" in jargon).

Each year, WHO develops recommendations on the composition of the vaccine based on surveillance conducted by the Global Influenza Surveillance Network. Because yes, as we said before, you have to get vaccinated annually. The effectiveness of vaccination is related to the degree of concordance between vaccine strains and wild circulating strains. On average, the efficacy of vaccination is 65%.

Flu vaccines are safe and well tolerated. The most frequent reactions are pain and redness at the site of administration, which disappear in 1 or 2 days without treatment. More rarely there is feverishness, muscle aches and discomfort within a few hours of vaccination, which also disappears spontaneously.

With everything and that, there are those who do not look at these vaccines with good eyes. WHO already included among the “10 main threats to health in 2019” the threat of influenza pandemic, highlighting the importance of vaccination, in addition to epidemiological surveillance and antiviral treatments. But he also noted that another major threat is the rejection or delay in the acceptance of vaccines, despite being available in health services.

A problem that, incidentally, not only affects the flu. The movements with disaffection and rejection of vaccines, paradoxically related to the great achievements made in the elimination of numerous diseases, are expensive. Because it is favoring the reemergence of some of them, such as measles, even in geographical areas where it had disappeared.

José María Bayas Rodríguez, former Associate Professor of Public Health, University of Barcelona

This article was originally published in The Conversation. Read the original.