Problems and Long -Term Side Effects of Covid Vaccines


Last Updated on 21 June 2024

When large groups of people started talking about the problems linked to the administration of covid vaccines, the phenomenon was defined vaccine hesitancy by the scientific community. We were in the middle of an unknown pandemic with effects that would have remained unknown for a long time. It was 2021.

But, today, just in a moment in which the covid 19 pandemic is considered over, in 2024, how are things really? The question is burning, because, although a lot of information about the possible problems and side effects of covid vaccines, nobody knows the truth, yet.

This article, hence, tried to shed a light on concerns, dangers, problems and long-term side effects of covid vaccines with the hope to provide comprehensive answers about the doubts that still surround the matter of covid vaccine boosters, viral vector and mRNA vaccines, the mix of Moderna and Pfizer vaccines and more.

Let’s turn this light on, then!

Problems with AstraZeneca Covid Vaccine


AstraZeneca was the first viral vector covid vaccine authorized in December of 2020 in the United Kingdom with the name of Vaxzervria. Millions of people received this vaccine and a few of them experienced a rare condition of blood clots along with abnormally low platelet levels, diagnosed as vaccine induced thrombotic thrombocytopenia. Only in the United Kingdom, after the first dose of the vaccine, the fatal cases of blood clots were 66, but lawsuits against the pharmaceutical company have been started by 75 claimants. In Italy, the confirmed victims were 22. The survivors also reported awful injuries and terrible disabilities caused by vaccine induced blood clots. In 2021, the Medicines and Healthcare Products Regulatory Agency in the UK, confirmed a possible link between AstraZeneca vaccine and the fatal condition of thrombocytopenia. According to the news reported on BMJ in March of 2023, Peter Todd, one of two lawyers handling claims, said that the vaccine complications included stroke, heart failure, and leg amputations. He also said the technology involved in the AstraZeneca vaccine was “risky.”

Moreover, the deadly adverse reactions to the AstraZeneca vaccine regarded young women and young men, while for elderly, the vaccine resulted safe and with no particular side effects.

Due to the announcement of the British Regulatory Agency, the vaccine administration was suspended and the product was totally removed (banned) from the market. However, we must say that AstraZeneca covid vaccine has never been approved in the United States by the FDA, because the British pharma company decided to withdraw its application.

Problems with Johnson & Johnson Vaccine

For many, Johnson & Johnson is the leading company of detergency products and soaps for babies. The fact that it started to make a covid vaccine in that time of pandemic emergency is already hard to believe.

But, yet, even this company entered the healthcare system with its own vaccine, called Janssen. The side effects of Johnson & Johnson viral vector covid vaccine are reported in a document of the Department of Public Health in California, where is clearly indicated that the risks include:

blood clots, rare severe allergic reaction and rare Guillain-Barre syndrome.

According to the public health document, blood clot symptoms began approximately 1–2 weeks after vaccination in males and females, across a wide age range of individuals 18 years and older; reporting has been highest for females ages 30 to 49 years old. For one to two weeks after receiving the vaccine, other symptoms may be shortness of breath, chest pain, leg swelling, persistent abdominal pain, severe headaches or blurred vision, easy bruising, or tiny blood spots under the skin beyond the site of the injection.

The document also says that there is a remote chance this vaccine could cause a severe allergic reaction (difficulty breathing, swelling of face and throat, fast heartbeat, bad rash all over your body, dizziness, weakness), which would usually occur a few minutes to one hour after getting the dose.

As regards the rare vaccine induced Guillain-Barre syndrome, the document explains that Guillain-Barre is an illness, usually triggered by an infection, in which the body’s immune system damages nerve cells, causing muscle weaknesses, or in the most severe cases, paralysis. Cases of Guillain-Barre Syndrome have largely been reported about 2 weeks after vaccination with Johnson & Johnson COVID-19 vaccine and mostly in males, many aged 50 years and older.

This vaccine consisted of a single dose. Eventually, the booster shots should be administered after six months, but only with the Pfizer vaccine. This was the decision of AIFA in Italy, made in 2021.

Today, the Johnson & Johnson covid vaccine is no longer available in the United States. In 2022, indeed, the US Centers for Disease Control and Prevention restricted the usage of this vaccine due to the risk of a rare and dangerous clotting condition called thrombosis with thrombocytopenia syndrome (TTS) after receiving it.

Problems with MRNA Vaccines

The aforementioned document revealed that MRNA covid vaccines are less risky and have less side effects than viral vector vaccines. Severe allergic reactions, blood clots and Guillain-Barre syndrome have never occurred with Pfizer and Moderna MRNA vaccines. That is why these two types of covid vaccines became the most used all over the world.

Talking to covid vaccinated people, I discovered that those who were vaccinated with Pfizer had less vaccine symptoms than those who received Moderna vaccine. After the second dose of Moderna, in fact, people experienced high fever, severe joint pain and a malaise that lasted for a couple of weeks. The malaise became more severe after the booster shot (third dose) with Moderna.

Any covid vaccine problems, indeed, could be linked to booster shots, frequently authorized with a different dose from the vaccines originally received.

Covid Vaccines and Booster Shot Mix

covid 19 vaccine

The FDA authorized the mix between Pfizer covid vaccine with Moderna booster shot, and Johonson & Johnson covid vaccine with a Mrna booster shot, both Pfizer and Moderna, but left people free of choosing individually to receive the same or a different covid vaccine as a booster dose. However, this option regarded the availability of booster doses. In Italy, unfortunately, people weren’t allowed to choose the same covid 19 vaccines as a booster shot, because, the only available booster doses were with Moderna, even for those who initially had received the covid vaccine with Pfizer or Johnson & Johnson, and even if, initially, the AIFA said that Johnson & Johnson covid vaccine could be mixed only with Pfizer booster dose. This is an incoherence which sounds strange.

In 2021, the national healthcare organizations in Italy confirmed that a Mrna booster shot was able to increase the efficacy of the single dose of Johnson & Johnson covid vaccine. Moreover, other official European studies confirmed that the covid vaccine and booster shot mix increased the immunogenicity and reactogenicity against Sars-Cov 2, and revealed that the highest levels of antibodies occurred with a Mrna booster dose, especially with Moderna. Hence, the mix between covid vaccine Pfizer and Moderna booster dose was strongly recommended, but, overall, a covid vaccination with a heterologous regimen was largely approved, because considered more effective than a homologous regimen. The same studies reassured about the safety of heterologous covid vaccination. But as regards the risks?

MRNA Covid Vaccines and Boosters. The Risks

In February of 2024, the World Health Organization commissioned the largest covid vaccine study on a cohort of 99 million vaccinated people. The study revealed that Mrna vaccines induced rare cases of heart inflammation (myocarditis). The highest rate of this condition occurred after the second dose of Moderna. The Moderna vaccine, according to the study, was able to induce an acute neurological disorder called encephalomyelitis. The condition occurred soon after the administration of the vaccine.

The risks of adverse covid vaccine reactions are higher with booster doses or repeated boosters. Moreover, these reactions regard both viral vector and Mrna booster shots.

Other clinical studies, indeed, have been performed across the globe, to verify the long-term vaccine induced conditions, and the emerging results are unsettling. A study conducted in Denmark revealed that covid vaccinated women reported changes in the menstrual cycle. According to studies performed in the United States, covid vaccinated people reported facial paralysis, neurological disorders and autoimmune diseases. However, the results relate to rare and acute cases. The US studies have been conducted both on health and autoimmune people. The most adverse reactions have been in people with previous autoimmunity.

The American studies found that the efficacy of covid vaccines decreases with booster shots, but there is also evidence that Covid spike protein and covid vaccines could be involved in the development of inflammatory processes, but it is not clear if the inflammation regards a vaccine induced inflammation or an autoimmune attack.

Indeed, for people who have autoimmunity covid booster shots are not recommended anymore. Covid spike protein and vaccine boosters could also cause brain inflammation. According to studies conducted until October 2022 and published on the website of the National Library of Medicine, the most-reported vaccine associated with encephalitis (38.5%) was AstraZeneca, followed by Pfizer (33.8%), Moderna (16.9%), and other covid vaccines. Most encephalitis cases occurred after the first dose of vaccination in 41 of the 65 patients undergone to the clinical trials (66.1%). The averaged time between vaccination and onset of symptoms was from 10 to over 16 days.

Encephalitis is a brain inflammation that can be successfully treated with corticosteroids and immunosuppressants. The disease is usually caused by a viral agent, such as the spike protein of covid 19 virus. Since adenovirus and MRNA vaccines have the same action mechanism of covid spike protein, they can cause the same brain inflammation. Just as the virus does, adenovirus and MRNA vaccines enter the cell with a molecule that resembles the spike protein, in order to trigger the reaction of our immune system.

This shocking result paves the way to other doubts raised by covid vaccinated patients, namely: can covid vaccines cause cancer? The doubt has been reported in another study published on the website of the National Library of Medicine, where the carcinogenic effect of covid 19 virus is hypothesized. Sars Cov 2, indeed, has the capacity to suppress the pathway which blocks tumors, because the cytokine storm that causes the severe acute respiratory syndrome shares the same inflammatory features of oncogenic cells. This is a long-term virus effect that has to be further investigated. But if covid 19 virus could cause cancer, can MRNA covid vaccines do the same? A partial answer is contained in a further study published in 2023, where it is reported that an elderly female developed a high-grade sarcoma after a few days from the second vaccination with Moderna covid vaccine.

Unfortunately, it is not clear, yet, if covid vaccines cause cancer or if cancer is a result of the inflammatory processes triggered by the vaccination that made the cells more tumor sensitive.

In the meanwhile, public health authorities deny that MRNA covid vaccines damage DNA, because they should break the cytoplasm of the cells, but this would be impossible with a MRNA molecule which gets immediately eliminated after triggering the reaction of the immune system. Hence, the carcinogenic hypothesis of MRNA covid vaccines could be linked to the inflammatory processes they are able to elicit in our body. Moreover, what SARS‑CoV‑2 and MRNA vaccines have in common is an immunosuppressant effect which could foster tumor development over time, as reported in a study published in ScienceDirect. This new study leads us to the burning issue of the long-term effects of covid vaccines.

Covid Vaccines: Long Term Side Effects

As regards this ending paragraph, I must admit I remained shocked by hypotheses and findings reported in recent clinical studies. One of them admits that variable neurological complications after the COVID-19 vaccination, despite the unproven causes, have been reported. These include functional neurological disorder symptoms, such as altered mental status (the so-called emotional symptoms from covid vaccines), autoimmune encephalitis (AE), acute disseminated encephalomyelitis (ADEM), dizziness, myalgia, fatigue, cognitive impairment, gait instability, facial palsy, Guillain–Barré syndrome (GBS), convulsions, strokes, transverse myelitis, chronic fatigue syndrome, and acute encephalopathy”.

Another study says that vaccination induces a profound impairment in type I interferon signaling, which has diverse adverse consequences to human health. Immune cells that have taken up the vaccine nanoparticles release into circulation large numbers of exosomes (extracellular mediators) containing spike protein along with critical microRNAs that induce a signaling response in recipient cells at distant sites. We also identify potential profound disturbances in regulatory control of protein synthesis and cancer surveillance. These disturbances potentially have a causal link to neurodegenerative disease, myocarditis, immune thrombocytopenia, Bell’s palsy, liver disease, impaired adaptive immunity, impaired DNA damage response and tumorigenesis.

However, to get confirmed as covid vaccine induced diseases, the side effects must onset within four weeks after receiving the dose.

I received the Pfizer covid MRNA vaccine in June and July of 2021, and I have had my early neurological symptoms in December of 2021. In January of 2022 I got Sars Cov 2 infection, and in the end of February of 2022, my neurological symptoms escalated. I was a vulnerable patient with autoimmune disorder and vitamin D deficiency, at that time. But I am sure that I’ll never learn the true cause of my current neurological disease. Today, I only know that I have been diagnosed with Parkinson disease.  What doctors said to me is that it is possible the inflammatory processes induced by a combination of covid vaccines and covid 19 disease have accelerated and anticipated the onset of a disease which would have anyway occurred late in life.  Hence, if for genetic conditions or autoimmunity, a patient develops cancer or neurological disorders in the late age, the subject may develop the same disease, earlier, for a covid 19 and vaccines induced inflammation.

But that is always a theory that needs further exploration.


As the current and aforementioned studies confirm, due to the urgency, vaccinations were approved based merely on the initial stages of clinical trials, without completion of all phases. The mRNA SARS-CoV-2 vaccines were brought to market in response to the public health crises of Covid-19. The utilization of mRNA vaccines in the context of infectious disease has no precedent.

Yes, because, until then, mRNA vaccines had been used only for cancer immunotherapy. The new usage was only approved to deal with the pandemic emergency.

This policy is demonstrated in a statement from Moderna, where is clearly written that Moderna COVID-19 Vaccine (2023-2024 Formula) has not been approved or licensed by the FDA, but has been authorized by the FDA, under an Emergency Use Authorization (EUA) to prevent Coronavirus Disease 2019 (COVID-19) in individuals 6 months through 11 years of age.

But that was the only way to save lives in the tragic context of an unexpected awful pandemic that, at the time, claimed over 20 million deaths. Public health authorities decided merely on the fact that the vaccine benefits surpassed the risks. And I add that they were right. There is no reason to criticize the efficacy of vaccines or to be hesitant towards them. My elderly mom every year receives her dose of flu vaccine and has never had symptoms or adverse reactions.

However, the approval of a new vaccine or a new medication usually takes from 4 to 10 years. For a common vaccine, six months could be enough, but, surely, a revolutionary technology such as MRNA vaccines will require further improvements over the years, to recheck what was overlooked in the tragic time of the pandemic, whose long-term impact will be discovered only in the years to come.

Author: Rosalba Mancuso
Rosalba Mancuso is a medical journalist, an international content writer credited at the University of Washington and a blogger born in Sicily. She is internationally appreciated for founding a network of four websites in English. On, Rosalba writes well researched and detailed health articles backed by her experience as a medical writer for pharma companies and as a PR assistant for a clinical analysis laboratory. She is also a member of the AHCJ, American Association of Health Care Journalists and Center for Excellence in Health Journalism. Her health magazine survives thanks to spontaneous donations, and sponsorships with brands and clinical organizations.