Heart attack. no
How the flu vaccine protects against strokes and cardiovascular diseases
Andrey Lomakin, Rostec State Corporation blog, Naked Science
Recently, there is more and more evidence that, in addition to protecting against infection and severe infection, flu vaccinations have other beneficial effects, for example, they protect against cardiovascular diseases, strokes and heart attacks. Andrey Lomakin, science adviser of the holding "Natsibio" of the Rostec State Corporation, Candidate of Medical Sciences, tells more about this in the material.
With the arrival of autumn cold and slush, an epidemic of influenza begins to occur in temperate latitudes. There are different ways to prevent infection, but regular annual vaccination has always been and will be the most effective. No vaccination helps to avoid the disease with one hundred percent probability, and the flu vaccine is no exception. But even if an immunized person catches an infection, it will be easier to proceed.
Protection is especially important for people from high-risk groups for severe infection. These include, among others, patients with diseases of the cardiovascular system. For example, the European Center for Disease Prevention and Control strongly recommends that these people be vaccinated annually.
What is the danger of influenza infection for people with CVD?
Doctors and scientists have long known that influenza can lead to complications from the respiratory system, such as severe bronchitis, pneumonia, secondary bacterial infections. The effect of influenza viruses on the cardiovascular system is not so obvious, and for a long time it was not possible to fully assess it. The fact is that many people have an increased risk of developing heart and vascular problems even before the disease. In addition, manifestations of cardiovascular complications often occur not at the same time when a person has the flu, but after a few weeks - therefore it is more difficult to track cause–and-effect relationships.
Nevertheless, during the research of recent years, it has been possible to prove some indisputable facts. Spikes in mortality from cardiovascular diseases often coincide with seasonal flu epidemics. Heart attacks in people who have had an infection occur six times more often a week after the flu than during the year before or after infection.
During one study, scientists analyzed 360,000 hospitalizations for the flu and found that 11.5 percent of patients had heart attacks at that time. Another study examined 90,000 cases of laboratory-confirmed influenza. The heart attack rate among these patients was almost the same as in the previous study – 11.7 percent.
Another study showed that one in eight patients treated at the clinic for influenza during the follow-up period had some kind of complications from the cardiovascular system. In intensive care wards, this figure was even higher – 31 percent. Seven percent of patients eventually died.
The cause of heart damage in influenza is an inflammatory reaction that develops in the body in response to infection. The cardiovascular system is under stress: the risk of blood clots increases, blood pressure rises. The virus can also affect the heart muscle: according to some reports, during seasonal influenza, myocarditis (inflammation in the myocardium – the heart muscle) is found in 1-5 percent of patients.
Because of this, it becomes more difficult for the heart to pump blood. Respiratory complications of influenza – pneumonia and respiratory failure – also significantly aggravate the manifestations of existing heart failure and arrhythmia. After all, the work of the heart and lungs is closely related: when one organ suffers, the second one also experiences stress.
The risk of strokes and heart attacks with influenza increases due to the fact that blood clotting is disrupted during infection, thrombosis increases. If there are already atherosclerotic plaques in the blood vessels, then blood clots form more actively on them. Because of this, blood flow to the heart muscle, brain tissue may be disrupted. The same thing happens with spontaneous rupture of an atherosclerotic plaque – its probability also increases during the flu.
By the way, the coronavirus that causes Covid-19 has a similar destructive effect on the heart and blood vessels, and this was also not so obvious at first. But later studies have shown that the risk of developing cardiovascular diseases remains elevated for a whole year after the infection.
It is clear that if a person is initially predisposed to the development of cardiovascular pathologies, or he already has a disease, his risks during infection are even higher. Vaccination helps to protect against them. And this is demonstrated in many scientific papers.
For example, a study conducted at Houston Methodist Hospital (USA) showed that adults who have been vaccinated against influenza are 37 percent less likely to need inpatient treatment, 82 percent less likely to go to the intensive care unit and spend an average of four days less there. Also, observing a group of patients, scientists found that the risk of cardiovascular complications due to influenza in vaccinated people is lower than in unvaccinated people - 2.9 versus 4.7 percent. In another observation, these figures were 9.5 and 19 percent, respectively.
Additional protection from the epidemic of the XXI century
Cardiovascular diseases are often called the epidemic of this century. They claim almost 20 million lives every year. Now it is the main cause of death worldwide. Among the most common causes of death of such patients are heart attacks and strokes. These conditions can often be prevented, there are many methods of prevention. And, as studies show, one of these methods can be vaccination against influenza.
For example, during one study, scientists found that people over 50 who were vaccinated against influenza during hospitalization had a 28 percent lower risk of heart attack during the following year than those who were not vaccinated. They also had a 47 percent lower risk of developing a transient ischemic attack, a condition often referred to as a mini–stroke. The risk of cardiac arrest was 85 percent lower, and the risk of death was 73 percent lower.
In 2020, the website of the American Heart Association presented the results of a meta-analysis that included 16 scientific studies and 237 thousand participants. According to the results, experts concluded that people with cardiovascular diseases who have been vaccinated against influenza are 18 percent less likely to die due to heart pathologies and 28 percent less likely to die from any cause. In addition, they have a 13 percent lower chance of encountering serious complications from the cardiovascular system.
Therapist Siva Yedlapati, lead author of the study, said: "Compare this effect with beta blockers and ACE inhibitors, which are used to lower blood pressure. Taking these drugs reduces mortality by 20-25 percent."
Another interesting observation: the protective effect does not depend on the dose of the vaccine. In patients who have been vaccinated with a standard dose, the risk of hospitalization and death from cardiovascular pathologies decreases in the same way as after the introduction of a standard dosage.
Experts also noted that these data showed nothing new. Reports that vaccination against influenza reduces the risk of heart attack, cardiac arrest, death from these conditions, and this protective effect persists for quite a long time, have appeared in the scientific literature for a long time. The results of the meta-analysis only once again confirmed how important it is to vaccinate people from high-risk groups. And cardiologists should be aware of this and explain to their patients the benefits of vaccination.
Isn't it dangerous to vaccinate "cores"?
In the vast majority of cases, vaccination against influenza is carried out by killed viruses that are unable to cause infection. To administer the vaccine, you need to give an injection in the shoulder. It is not dangerous for people with cardiovascular diseases. Most often, side effects are limited to a slight pain at the injection site, muscle spasms and an increase in body temperature – they do not always happen and pass quickly.
People with cardiovascular diseases and those over 65 years of age are not recommended to administer only nasal (in the form of injections into the nostrils) flu vaccines. They include live weakened viruses.
The main contraindications to immunization are acute infections, high fever, allergic reactions to previous flu vaccinations. In very rare cases, after vaccination, a complication develops in the form of Guillain-Barre syndrome (the flu itself leads to it much more often), such people also cannot be vaccinated again. Allergy to eggs is a common horror story – it is not a contraindication. Modern vaccines are very well purified.
It is better to get vaccinated in September or October – the seasonal epidemic has not yet entered into force. The procedure is carried out by the polyclinic at the place of attachment. A referral for vaccination is issued by a general practitioner or a general practitioner. Mobile vaccination points are also operating in many regions – in large shopping malls and public service centers.
For vaccination, drugs that meet international quality standards and the requirements of the Russian pharmacopoeia are available under the trade names SOVIGRIPP and Ultrix Quadri. Both vaccines have a wide practice of application in Russia, contain current strains of influenza viruses recommended by the World Health Organization for the epidemic season of 2022-2023. The drugs have undergone a full range of preclinical and clinical studies.
Ultrix Quadri, a quadrivalent vaccine of the latest generation, includes four current strains of influenza viruses instead of three: two strains of A – H1N1 and H3N2 viruses and two strains of group B influenza viruses. In accordance with the recommendations of the World Health Organization, the drug contains 15 micrograms of hemagglutinin (antigen) of each strain in one dose – only 60 micrograms of antigen. The supply of vaccines for NCPP to all subjects has been provided by the holding "Natsibio" of Rostec State Corporation since 2015.
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