Image by ronstik from Pixabay
Image by ronstik from Pixabay

Changing the way we jab might help stop post-vax fatigue

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Peer-reviewed: This work was reviewed and scrutinised by relevant independent experts.

Experimental study: At least one thing in the experiment was changed to see if it had an impact on the subjects (often people or animals) – eg: changing the amount of time mice spend on an exercise wheel to find out what impact it has on weight loss.

Observational study: A study in which the subject is observed to see if there is a relationship between two or more things (eg: the consumption of diet drinks and obesity). Observational studies cannot prove that one thing causes another, only that they are linked.

Animals: This is a study based on research on whole animals.

Cells: This is a study based on research in micro-organisms, cells, tissue, organs or non-human embryos.

Swapping from an intramuscular injection to one that goes just under the skin might help reduce fatigue after a COVID-19 vaccination according to an international study in mice. The research initially looked at blood samples from people vaccinated for COVID-19, finding that people who had an increased chance of post-vaccination fatigue also had molecular markers in their blood related to the activity of their immune cells. The researchers then compared under the skin injections to intramuscular injections in mice, finding that the injections which were given just under the skin were able to give the same level of protection but a lower chance of adverse effects like fatigue.

Journal/conference: PLOS Biology

Link to research (DOI): 10.1371/journal.pbio.3001643

Organisation/s: Duke-NUS Medical School, Singapore

Funder: This study was supported by the National Medical Research Council (NMRC) Open Fund-Large Collaborative Grant (OFLCG19May-0034) and Senior Clinician-Scientist Award (MOH- 000135-00) to E.E.O, and the Open Fund-Young Investigator Research Grant (MOH-OFIRG18nov- 0004) to R.D.A. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Media release

From: PLOS

Peer-reviewed         Observational study; Experimental study            Cells; Animals

New study points to potential strategy to reduce fatigue after COVID-19 vaccination

Mouse experiments suggest a switch from intramuscular to subcutaneous injection may ease fatigue

Despite their strong effectiveness against SARS-CoV-2, mRNA-based COVID-19 vaccines are associated with adverse post-vaccination effects, such as fatigue; how can this be avoided? In a new study publishing May 31st in the open-access journal PLOS Biology, Ayesa Syenina of the Duke–NUS Medical School in Singapore and colleagues report that a new analysis of blood samples from people vaccinated for COVID-19 has identified distinct molecular characteristics linked to an increased likelihood of post-vaccination fatigue. Additionally, experiments in mice suggest that switching the vaccine injection strategy could potentially ease such adverse effects.

Adverse post-vaccination effects may influence people’s willingness to get vaccinated or receive a booster dose, hampering efforts to reduce the spread and severity of COVID-19. However, the molecular underpinnings of adverse post-vaccination effects have been unclear.

To improve understanding, Syenina and colleagues analyzed blood samples from 175 healthcare workers who received BNT162b2, the Pfizer-BioNTech COVID-19 vaccine. Specifically, they used the blood samples to analyze a snapshot of each participant’s gene expression, or which genes are turned on or off.

This analysis revealed that people who experienced moderately severe fatigue after vaccination were more likely to have higher baseline expression of genes related to the activity of T cells and natural killer cells—two key cell types in the human immune system.

The researchers also tested two different vaccination injection strategies in mice. Some mice received BNT162b2 through intramuscular injection, the current method used for human patients, in which the vaccine is injected into the muscles. Other mice received a subcutaneous injection, in which the vaccine is injected into tissue just under the skin.

After vaccination, compared to mice that received intramuscular vaccination, mice that received subcutaneous vaccination showed immune-system responses that are in line with a lower likelihood of adverse effects such as fatigue. However, subcutaneous injection did not appear to compromise the protective effects of vaccination.

Further research will be needed to build on these findings and explore their clinical significance. Still, they boost understanding of post-vaccination fatigue and offer a potential strategy to reduce its likelihood.

Coauthor Eng Eong Ooi adds, “This study provides a first insight into the molecular basis of a side effect that many have experienced following mRNA vaccination. We hope that this finding would spur more studies to fully understand the underpinning mechanisms behind vaccine-associated side effects and collectively contribute to developing even more tolerable vaccines.”

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