How difficult it is to investigate the side effects of Covid-19 vaccines we have been seeing for some time now with the AstraZeneca case and the succession of stops or restrictions imposed by European countries on the use of the Anglo-Swedish vaccine, despite the reassurances of the ‘Ema (European Medicines Agency). Norway, Denmark and the Netherlands have suspended – temporarily – its administration, Germany has limited it to people over 60, France to those over 55, Greece from 65 and over. In Italy the Undersecretary for Health Pierpaolo Sileri he told Radio 24 that the EMA could indicate not to use AstraZeneca for certain categories of people, adding however that “there is no doubt that there is a positive risk-benefit ratio”.
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Covid, the vaccine works less if you are stressed
by Valentina Arcovio
His words have been confirmed to the breaking latest news by Fabrizio Pregliasco, medical director of the Irccs Galeazzi Orthopedic Institute of Milan and virologist at the University of Milan, who underlines how much the benefits deriving from vaccination clearly outweigh the risks and that the understanding of the causal mechanism that would determine the danger of vaccination.
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Covid vaccine: the Italian anomaly of adverse reactions
by Giuseppe del Bello
But why is it so complicated to shed light on possible “reactions” to Covid-19 vaccines? This is discussed in an article just published in Nature. It is extremely difficult to prove that the so-called ‘adverse event’, i.e. a medical problem that arose after immunization, is caused by the vaccine itself. Researchers must strive to establish causation, a process that could take years, while at the same time being careful about how news is conveyed in order not to fuel anti-vaccine movements or arouse fear in people.
In most cases, there are no laboratory tests to evaluate this type of adverse event and at first you only have to count on the timing: a person receives the vaccine and after days or weeks a reaction occurs. The researchers then conduct studies to determine the rate of adverse events in vaccinated populations by comparing it to the likelihood that the same events will occur in people who have not received the vaccine. And they must simultaneously shed light on the mechanism that could have caused the reaction.
Covid vaccine: scientists’ answers to all doubts about immunization
by Irma D’Aria
The solution is never immediate, indeed the study could last decades, as was the case during the H1N1 swine flu, when public health agencies in Sweden and Finland sounded the alarm about an increase in the rate of narcolepsy – a disorder of the chronic and debilitating sleep – in children who had received a dose of Pandemrix, an H1N1 vaccine.
Episodes of narcolepsy have been reported at a rate of about 1 case in 18,400 doses, and researchers speculated that a component of the vaccine used to boost the body’s immune response, called an adjuvant, could cause an unintended immune response that triggered the disease. . Early studies suggested that Pandemrix increased the risk of narcolepsy in some age groups, but the results were too variable to draw general conclusions. Even today, scientists have not reached a unanimous opinion on the Pandermrix-narcolepsy correlation.
Covid vaccine: Pfizer works well on teens
by Valentina Arcovio
Covid-19 vaccines were tested in clinical trials with thousands of participants before governments authorized their widespread use. These clinical trials are “set up to answer questions about efficacy and to evaluate the rate of fairly common adverse events,” such as injection site pain or headache, he says. Hilda Bastian, an independent scientist studying evidence-based medicine in Victoria, Australia.
But even the largest clinical trials are not designed to detect extremely rare side effects, which could occur in less than 1 in every 10,000 vaccinations. Since hundreds of millions of people are now vaccinated against COVID-19, it makes sense that even occasional events, such as severe allergic reactions or blood clots, start showing up in safety reports, Bastian says. The challenge now is figuring out which of these events are actually vaccine-related.
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Swollen lymph nodes after the Covid vaccine
In the United States, the National Institute of Allergy and Infectious Diseases has begun organizing a clinical trial to understand the allergy risks of Covid-19 messenger RNA (mRNA) vaccines. The mRNA vaccine manufactured by Pfizer in New York City and BioNTech in Mainz, Germany, is associated with a rate of five cases of severe allergic reaction per million doses, and that manufactured by Moderna in Cambridge, Massachusetts, is associated with a rate of three cases per million doses. Those affected appear to be mainly women and people with a history of allergies. Stacie Jones, an allergist and immunologist at the University of Arkansas for Medical Sciences at Little Rock, is conducting a study to understand the proportion of these reactions that occur in people with a history of allergies, compared to a control group. If the study looks at an increase in the rate of severe allergic reactions, it will allow researchers to “know who is at risk and define that risk” so doctors can provide better advice.
Covid, just one dose of vaccine is enough for the recovered?
at Federico Mereta
Currently, public health agencies track potential side effects through reporting systems such as the World Health Organization’s VigiBase platform, EMA’s EudraVigilance, and the U.S. Vaccine Adverse Event Reporting System. Many countries have systems where the public and healthcare professionals can submit reports on side effects that occur.
This type of surveillance can detect signs of rare adverse events, but most systems are not designed to determine the exact cause because they do not have a comparison group to track adverse events that occur in unvaccinated populations. A more complete understanding of vaccine safety could be gained from active surveillance systems that collect data on adverse events – both baseline and post-vaccine rates – from electronic health records and not from people who report them directly.
The combination of active surveillance and targeted clinical trials is important to ensure the safety of current Covid-19 vaccines, for annual boosters and vaccinations that may be needed for the duration of the pandemic and to have an extra key to fighting any variants.
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