Everything about the flu

Could the virulence of A / H1N1v increase? What are the side effects of the vaccines? How is a pandemic different from an epidemic? These are just some of the most frequently asked questions about flu, and there’s a lot of concern for good reason.

How did WHO know about the impending flu pandemic?

Larger changes in influenza A viruses leading to entirely new subtypes are rare, usually due to the exchange of larger pieces of genetic material between human or human and animal influenza viruses (e.g., avian or swine influenza viruses), or the adaptation of the animal influenza virus to infect humans ( e.g. avian influenza virus). Such new virus subtypes or variants, which are capable of being transmitted easily from human to human, have the potential to cause a pandemic, since immunity (even residual) in humans to infection with this virus is low or low. A pandemic occurs suddenly – millions of people are sick worldwide in a relatively short time (e.g. 2-3 months) – therefore, after its outbreak, there would be too little time for countries to properly prepare and minimize its consequences for citizens and the functioning of the entire state. In order to provide early information about a potential threat, which allows for proper preparation for the fight against a pandemic, WHO closely monitors influenza in humans and animals and the different stages of the pandemic’s development (there are 6): starting with the emergence of new virus subtypes with potential in humans. pandemic (phase 2 and 3), by acquiring the ability to spread easily from person to person (phase 4) and to cause local epidemics on one continent (phase 5), until phase 6, which marks the outbreak of a pandemic.

Intensive preparations, coordinated by the WHO, for a possible pandemic caused by the A / H2003N5 avian influenza virus were carried out since 1, as in Hong Kong and China isolated cases of A / H5N1 influenza (the so-called avian influenza) were noticed in people who had close contact with sick birds. The mortality of influenza A / H5N1 in humans was very high. Therefore, national pandemic management plans were developed, flu drugs were stocked, and production and clinical trials of prototype A / H5N1 pandemic vaccines began. Fortunately, the A / H5N1 virus has not yet acquired the ability to easily infect humans and transmit effectively from person to person. In spring 2009, however, reports of serious illnesses and deaths in Mexico from the new influenza virus A / H1N1v (known as swine flu; see below) were confirmed in the United States and other countries of the Americas, Europe, Asia and Australia. Consequently, in June 2009, the WHO announced the 6th phase of the A / H1N1v influenza pandemic.

Could the virulence of A / H1N1v increase?

The A / H1N1 subtype of influenza virus is known to change rapidly, and the more virus circulating in a population, the more likely it is that a significant change will occur. An additional problem is the occurrence of interspecific infections – e.g. pigs are infected by human and avian influenza viruses, which enables the exchange of genetic material and the formation of hitherto unknown subtypes of the virus. In Norway, an epidemic of A / H1N1v influenza has recently been detected in pigs on farms and the source of the infection in the animals was sick people. The situation therefore requires close monitoring.

On the other hand, there is a real risk of the spread of A / H1N1v virus resistant to antiviral drugs, as their massive, uncontrolled use may lead to the selection of resistant strains. Such A / H1N1v strains have already emerged, but fortunately, for the time being they are only a small percentage of the viruses circulating in the population and are less infectious.

What is a seasonal flu epidemic and how is it different from a flu pandemic?

Every year around the world – in the temperate zone during the cooler season (late autumn to early spring) – there is a wave of seasonal flu cases (the so-called flu season or flu epidemic season). In the following years, the seasonal influenza viruses that infect humans are slightly different from those dominating in the previous season, and therefore the immune system is not sufficiently recognized by the immune system even for those who have suffered from influenza in previous years. You can get sick with the flu many times (even every year). However, some residual immunity remains, so the disease may be milder or the infection may even be asymptomatic. The severity (number of cases), duration, onset, and peak of flu season can vary significantly from year to year depending on many factors (including the degree to which the virus differs from previous seasons). In some flu seasons, the number of cases in a specific area (e.g. in a country) is much higher than usual, and then it is referred to as an epidemic (Greek epi: haunting + demos: people). Depending on the assessment of the situation, the authorities may declare an epidemic by an administrative decision, which entails the use of formalized prevention methods by the sanitary and epidemiological services of the country (e.g. closing schools and workplaces, banning gatherings and canceling mass events, closing borders, compulsory vaccination, forced treatment and isolation of sick, etc.).

Every dozen to several dozen years, as a result of major changes (see below), completely new subtypes of the influenza virus, significantly different from the previous ones, arise. The vast majority of people have never come across such a virus (in extreme cases no one), so almost the entire population is susceptible to falling ill because the human immune system is unable to recognize it. These new subtypes of the influenza virus, which have acquired the ability to spread easily from person to person, are spreading rapidly and causing epidemics not only locally (on one continent) but in several, and even worldwide. The number of cases during the flu season is then many times greater than during the usual epidemic of seasonal flu, and people of all ages are sick. Such a global epidemic of unprecedented intensity (affecting more than 20% to more than 40% of the population) caused by a completely new subtype of influenza virus is called a pandemic. A pandemic is declared by the World Health Organization (WHO) based on strictly defined criteria (see below). However, the severity of the course of the flu does not matter for the declaration of a pandemic, only the geographical scope and the expected scale of the disease are decisive.

The media reported deaths following pandemic influenza vaccination. Were they caused by the vaccine?

It is worth remembering that during mass vaccination of millions of people, vaccination will accidentally coincide with various adverse events that would also occur without vaccination, including deaths from natural causes or coexisting diseases. In each such case, the relevant institutions (e.g. EMEA, ECDC, national drug registration offices) must clarify whether there is a repeatability in many people vaccinated with this preparation, indicating a cause-effect relationship, or only a coincidence – occurrence at a similar time two unrelated events (which is the most common). Each report of a suspected serious adverse event is taken very seriously and immediately explained in detail.

In countries where mass pandemic influenza vaccination has started, single death reports have occurred within days of vaccination (Sweden, Germany, France). However, no causal link to vaccination was established in any of the cases, and in most of them a careful investigation revealed another more likely cause of death (eg, severe underlying disease). In Sweden, out of more than 2 million doses of vaccine administered, 8 such reports have been registered – all in the chronically ill, mostly elderly people. Necropsy results – available in 4 cases – revealed other causes more likely than vaccination. Despite the fact that almost 1/4 of the population has already been vaccinated in Sweden, the number of deaths in this group did not differ from the expected value based on observations preceding the vaccination campaign (approx. 220 deaths a day). In the United Kingdom, the mass vaccination program for at-risk groups was launched on October 21 and until November 13 this year. no reports of deaths following administration of the vaccine have been registered.

People die every day for a variety of reasons, so deaths following vaccination during mass campaigns must not be automatically considered as a vaccination effect. Observations prior to the UK pandemic vaccination campaign indicate that for 10 million people vaccinated statistically, 6 sudden, unexplained deaths unrelated to vaccination can be expected within 6 weeks after vaccination. However, each such report is carefully monitored, and the cause-and-effect relationship is explained by institutions responsible for vaccination safety.

Why is thimerosal in some vaccines and is it safe?

Thiomersal is an organic mercury compound (contains approx. 50% mercury ethylene) with very strong antibacterial and antifungal properties. It is present in multi-dose packages of 2 out of 3 EMEA-registered pandemic influenza vaccines (one at 2,5 or 5 µg / dose and the other at 50 µg / dose) to protect the formulation from bacterial contamination during production and after reconstitution and preparation for use. It is also in a pandemic vaccine produced and registered locally in Hungary, and in a multi-dose vaccine registered in France. Thiomersal does not contain the vaccine available in single-dose packages 1 of 3 pandemic influenza preparations registered in Europe and the French pandemic vaccine, and none of the seasonal influenza vaccines available in Poland. Thiomersal has been used in some medicines and cosmetics as a preservative since the 30s. . XX century. After administration of thiomersal at the dose contained in vaccines, mercury ethylene is excreted within a few days from the body, even in infants, and its concentration in the blood does not exceed the limits established for the presence of mercury methylene in the environment and food (see lower). A lot of scientific data from over a dozen studies conducted independently by researchers in different countries agree that the amount of thiomersal used in some vaccines is safe for humans (both children and adults, including pregnant women) and does not cause side effects. Rarely (1% of adolescents and adults) allergic skin reactions at the site of contact with thimerosal have been reported, but even in allergic individuals, they are very rare after vaccination. In response to hypothetical allegations, many scientific studies have also confirmed the safety of thimerosal vaccines for babies born to women vaccinated during pregnancy, and ruled out a real risk of a negative impact of thimerosal contained in vaccines on the development of young children. The most important source of human exposure to mercury in Europe today is food – especially certain species of fish (e.g. tuna, swordfish, mackerel) and marine crustaceans – in which mercury is present in the form of methylene. Mercury methylene, compared to ethylene, remains in the human body much longer and in a sufficiently high dose can lead to poisoning and damage to the nervous system. All safety standards, including the blood concentration standard mentioned above, are set for mercury methylene. Considering the continuous human exposure to mercury in food throughout life (mainly in the form of methylene), the Joint Committee of Experts on Food Additives FAO / WHO (JECFA) was established in 2004 by a safe dose of chronic dietary mercury per 1,6 µg / kg body weight / week (equivalent to 96 µg of mercury for a 60-kg human). This value is many times lower than the dose of mercury methylene, which leads to poisoning.

What are adjuvants and are those in some vaccines safe?

An adjuvant is a substance that increases the immune response and makes the body respond better to the vaccine given. Thanks to this, a better vaccination effect can be achieved or a similar effect can be achieved after a dose of the vaccine several times lower. The latter benefit of adjuvants is particularly important in the face of an influenza pandemic, when hundreds of millions of doses of the vaccine need to be produced in a short period of time in order – in line with the recommendations and expectations of the WHO – to quickly ensure fair access to these preparations and to satisfy the needs of as many people at risk as possible. the needs of governments around the world. Already a few years ago, during the work on pandemic vaccines against A / H5N1 avian influenza, WHO recommended that manufacturers use adjuvants, thanks to which vaccinations will be able to cover several times more people.

Several pandemic flu vaccines in use today around the world already contain adjuvants. Two of the three EMEA-registered formulations in Europe contain an oily substance in water (vitamin E and / or squalene), and one vaccine locally registered in Hungary contains an aluminum compound.

Aluminum-based adjuvants have been used successfully in various vaccines around the world for over 60 years and are very well-proven safe. More modern squalene-based adjuvants were developed over 12 years ago and their safety has been proven in more than 70 clinical trials with various vaccines in over 30 people (including neonates, infants and toddlers). Since 000, they have been used in some seasonal influenza vaccines for the elderly, registered in 1997 countries around the world (including 23 in Europe). More than 12 million doses of squalene-based adjuvant vaccines have already been administered, and no alarming signals have been registered.

Squalene is a natural compound found in plants and produced in the liver of animals and humans. It is a building component of human cells and an intermediate product of cholesterol metabolism; it is constantly present in the blood of people. It is present in fish oil, vegetable oils and olive oil, and after consumption of 60 – 80% of squalene is absorbed from the gastrointestinal tract. Some healthy people naturally contain weak antibodies to squalene, and studies have shown that administering a vaccine containing squalene as an adjuvant to humans does not increase this natural level (i.e. it does not produce antibodies against the squalene in the vaccine).

The hypothesis that squalene-based adjuvant vaccines allegedly relate to the occurrence of symptoms of the disease called Persian Gulf syndrome in soldiers who fought in the first Iraq-Kuwait war was disproved many years ago.