[ad_1]
Two women became seriously ill after receiving a candidate vaccine against Sars-CoV-2. This could indicate a side effect, but it doesn’t have to be. What to know about vaccination complications.
An effective vaccination would simplify a lot in the days of Corona: women with their newborns in a maternity ward in Manila, Philippines.
The world has been waiting for months for a vaccine against the new coronavirus. This, for which the conviction, could finally end the pandemic. President Trump also hopes to be re-elected in November with rapid success in vaccine development.
However, no one knows how effective the long-awaited vaccination against Sars-CoV-2 will be. And will it be safe too? A vaccine from the University of Oxford recently rekindled the discussion about side effects. The pharmaceutical company AstraZeneca, which participated in the evaluation, had to interrupt its study program after two women became seriously ill after vaccination.
In one case there was talk of inflammation of the spinal cord (transverse myelitis), in the second woman the diagnosis seems less clear. Furthermore, it has not apparently been proven whether the test subjects’ symptoms are related to the vaccine. Thus, two central questions arise: How common are serious side effects after vaccines? And how do they arise?
Normal reaction or complication of vaccination?
According to the Federal Office of Public Health, serious side effects or permanent damage after vaccines are very rare, but they do exist. Normal vaccination reactions such as redness, swelling and pain at the injection site and general reactions such as fever, headache, pain in the extremities and general malaise must be distinguished from these undesirable vaccination symptoms. These reactions are an expression of the desired confrontation of the immune system with the vaccine.
There is an intensive search for actual complications of vaccination in clinical approval studies, such as those currently running with various Sars-CoV-2 vaccines. “But not all potential problems can be identified with this,” says internationally recognized vaccination expert Claire-Anne Siegrist of Geneva University Hospital. This is due to the rarity of such complications.
Siegrist does an example calculation. In the case of a serious and life-threatening side effect, which occurs less than once in 100,000 vaccinated people, more than 300,000 people must be immunized to reliably detect the complication. For the professor, therefore, it is clear: “A vaccine against Sars-CoV-2 must first be administered to people who are at high risk of a severe course of Covid-19.”
Most of the adverse effects of vaccines are caused by an immune system response. At best, it is a harmless inflammation that is part of the normal reaction to vaccination. More serious, but almost always treatable, are allergic reactions. These are often not activated by the actual vaccine, but by added active amplifiers and other substances, Siegrist says. Sars-CoV-2 vaccines with viral genetic material (DNA and RNA vaccines) could have an advantage here over conventional (weakened virus, virus proteins) or vector-based vaccines.
However, according to the doctor, a bigger problem is autoimmune diseases that can be triggered by vaccines. This happens through a phenomenon called molecular mimicry. The immune system acts falsely against the body’s own components. The reason: the structures attacked are fatally similar to the components of the vaccine. This autoimmunity is often directed against the nervous system. Clinically, inflammation of the nerves (Guillain-Barré syndrome), the spinal cord (myelitis) or the brain (encephalitis) may be in the foreground.
Statistics help investigate causes
Attacks on the body’s own molecules are not only triggered by vaccines. Many viral and bacterial pathogens can also trigger harmful autoimmune reactions. The connection in Guillain-Barré syndrome, a paralysis that usually arises in the legs, has been well studied. The syndrome has long been tested in Covid-19 patients.
Therefore, the inflammation of the spinal cord in the AstraZeneca study does not necessarily have to be related to the vaccine. Because causal assignment is difficult in individual cases, only statistics usually help. If it turns out that serious autoimmune disorders occur more often in vaccinated people than would be expected without the vaccine, then the vaccine should be the trigger. Otherwise, other factors are more likely to have triggered the symptoms.
This statistical evidence was successful with Pandemrix, a flu vaccine that was used against the swine flu pandemic in many countries in 2009. In Finland and other European countries, the vaccine caused an increase in a very rare autoimmune disease of the central nervous system. (narcolepsy) in children. “Hitherto unknown side effects cannot be anticipated,” emphasizes Siegrist. It is very important to rigorously monitor safety even after the vaccine has been approved.
Another source of potential vaccination complications are certain antibodies that are formed after immunization with Sars-CoV-2 vaccines. These are not the desired neutralizing antibodies, which appear to be essential for a protective effect. From previous observations, also with coronavirus, we know that immunization also produces non-neutralizing antibodies. By facilitating infection and / or strengthening the immune response, these proteins can make people who have been vaccinated even sicker after infection than without the vaccine.
Researchers have demonstrated this effect with the Dengvaxia dengue vaccine, prompting the manufacturer Sanofi to issue a warning in 2017. Antibody-dependent boost should receive the most attention when evaluating new Sars-CoV-2 vaccines, the researchers write in the journal “Nature”.
“Surprisingly safe”
Despite such risks, vaccines are generally “remarkably safe.” This is the conclusion of the scientists. in an analysis that was just published in the Annals of Internal Medicine. To do this, they examined changes in safety information for approved vaccines that had occurred in the United States over the past twenty years. The modifications are based on the US Vaccination Reactions Reporting System (VAERS). The security system has been in use since 1990 and generates around 30,000 reports a year.
Throughout 1999, a single vaccine had to be recalled for safety reasons. This is Rotashield, the first vaccine against rotaviruses, which cause severe diarrhea in young children. The warning signs in VAERS had drawn experts’ attention to a much higher risk of rare but potentially fatal intestinal invasions. In children under one year of age, the risk of developing the disease was 20 to 30 times higher than without vaccination. The CDC has estimated that for every 10,000 children vaccinated, one or two additional intestinal invasions should be expected.
However, according to vaccine safety specialist Daniel Salmon of the Johns Hopkins Bloomberg School of Public Health in Baltimore, USA, few concerns about vaccination are based on scientific evidence. The example of Lymerix, the first and so far only human vaccine against borreliosis, shows that public pressure can also bring down a vaccine. Approved in 1998, the manufacturer took it off the market four years later.
Reports of joint swelling had broken the neck from the vaccine. The possible side effect was exploited without restriction in media reports and by opponents of vaccination, and legal actions were brought against the manufacturer. The company eventually recalled the vaccine from the market, although health authorities found no increased risk of reported complaints in the pre- and post-marketing data. For experts, the Lymerix story is a cautious example of how irrational the world can be.
This also dovetails with the results of a recently published survey on public confidence in vaccines. Consequently, approval is generally low in Europe, although there are large regional differences. In Finland, for example, a record 66 percent of respondents said they thought vaccines were safe, while the approval rate in Lithuania was 19 percent. Researchers see the rapid spread of false information about vaccines and the fact that there are exaggerations regarding the real risks as reasons for the low level of confidence in many places. Both arouse fears and sow doubts and mistrust. These mechanisms should also play a role with respect to Sars-CoV-2 vaccines.
Follow the NZZ science desk Twitter.
[ad_2]
