Covid-19: why do vaccines affect each person differently?

The Covid-19 vaccine was one of the most anticipated events last year. When it was her turn, in July 2021, Rosa received a first dose. As usual, she spent a few hours with a fever. However, she knew that these were common symptoms and she did not experience any concern.

What did surprise her is that some of her co-workers showed no symptoms after inoculation. Also that other friends of hers had general malaise. This has been a familiar scenario for many people. Is there an explanation for such different reactions to vaccines?

Immune response against coronavirus infection

To assess why these vaccines affect each person differently, it is necessary to know the immune response mechanisms against SARS-CoV-2 infection. And that implies differentiating innate immunity from cellular and adaptive immunity.

  1. innate immunity. When an innate response is produced against this virus, the number of neutrophils can increase, lymphocytes decrease and the levels of some proteins such as cytokines vary. The call cytokine storm is the uncontrollable release of cytokines in patients with severe conditions. This causes viral sepsis and inflammation-induced multi-organ damage.

    In addition, it can trigger other complications such as acute respiratory distress syndrome and potentially death. In contrast, the innate immune system produces type I interferon, which interferes with virus replication and induces the adaptive response.

  2. Cellular and adaptive immunity. In patients with Covid-19, the response of B lymphocytes (antibody producers) occurs concomitantly with the response of helper T cells.

    The B cells produce antibodies, first against the virus coat protein and then against the spike protein, which are effective in neutralizing the virus. However, some patients do not develop antibodies and are susceptible to reinfection.

    For their part, T-cell responses have been associated with milder symptoms in many infections. These have a crucial role in eliminating virus-infected cells and establishing long-term immunological memory pools that can respond to SARS-CoV-2 variants, including omicron.

Effectiveness of vaccines in people with diseases

No vaccine is 100% effective. There are different factors related, some with the virus and others with people, that can affect the response to vaccination. Even environmental factors such as pollution could interfere with the transmission of SARS-CoV-2 and, therefore, in our response to infection or vaccinations.

Therefore, it is important to identify the mechanisms associated with the protective response or with the disease in vaccinated people.

Along these lines, a study carried out with the Hospital General Universitario de Ciudad Real (still under review) identified that antibodies were the most abundant proteins in the serum of people vaccinated against Covid-19 and infected with SARS-CoV-2. . But vaccinated and infected patients with severe symptoms had autoantibodies and risks of allergy and thrombocytopenia. These results show how the response to the vaccine against the disease can vary between people.

On the other hand, in a study with 1,271 participants, the level of antibodies after vaccination varied according to the condition of the participants: healthy health workers (92%), infected with HIV or AIDS (80%), with autoimmune conditions or tumors solid (79%), with hematological neoplasms (50%) and transplanted (31%).

Likewise, it is known that most patients with inflammatory bowel disease develop an initial response to vaccination against Covid-19. However, the same does not happen with older patients and those with immunomodulatory treatments, who have more limited responses, and may need more than one additional dose of the vaccine. This indicates that additional strategies are needed to protect immunocompromised patients.

Another disease that has been studied is tuberculosis. Thus, it has been seen that mice infected with the pathogen that causes tuberculosis, Mycobacterium tuberculosis, are resistant to acute Covid-19. Nevertheless, current vaccination (BCG) against tuberculosis (which induces a trained immune response against other pathogens) may have a negative effect on the response to SARS-CoV-2depending on the time elapsed since vaccination.

Smoking and diet

Smoking and comorbidities were associated with 35% and 55% lower antibody levels. Also at 43 and 45% lower neutralization on response to vaccination against Covid-19, respectively.

Diet can also be a factor. affects disease development and possibly response to vaccination. When a person becomes infected with the coronavirus, the composition of their gut and lung microbiota is affected. As a consequence, there could be negative effects on the protective response against the virus.

Therefore, plant-based micronutrients, nutraceuticals, probiotics and antioxidants could play a role in boosting the immune system against the virus and in response to vaccination, especially in vulnerable people.

Personalized vaccination recommendations

Aside from very rare serious side effects, some vaccines may cause short-term fever, muscle aches, or fatigue. These side effects associated with vaccination can also affect the effectiveness of the vaccines and vary from person to person. For example, gout is associated with poor outcomes in Covid-19 and gout outbreaks can be triggered in response to vaccines, primarily in the first month after each dose.

Therefore, as a team from the University of Barcelona has just shown, it may be necessary to personalized vaccination recommendations, adapted to each person’s history and lifestyle.

Now one of the main challenges with SARS-CoV-2 is to optimize the antigen for the vaccine. Whether the vaccine should target the entire spike protein or focus on the receptor-binding domain is still being debated. Likewise, the duration of protection and the optimal administration schedule are being investigated. Another challenge is the side effects associated with vaccines. We need to better understand why vaccines affect each person so differently.

Openly shared research, innovation, and global coordination are key components to developing effective vaccines, optimizing administration schedules, and ensuring their equitable distribution globally.

Jose de la Fuente, Research Professor at the CSIC. Molecular Biology and Biotechnology, Castilla-La Mancha university Y Christian GortazarProfessor of Animal Health at IREC, head of the SaBio group, Castilla-La Mancha university

This article was originally published on The Conversation. read the original.

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