The COVID-19 virus began its sweep of the globe over a year ago, and people have been subject to its grave effects far and wide in the months that followed. At the time of writing, the virus has claimed over two and half million lives – and for the ~70 million people who have contracted the virus and survived, the negative health repercussions are still hitting hard.
In December of 2020, some hope was given to people all over the world when the first person received the Pfizer vaccine in the UK. Since then, more vaccines have been developed and now, almost 100 million people are fully vaccinated against COVID. The vaccine rollout has been a huge relief for everyone who’s ready to return to normal life and reduce their COVID-19 risk. But is the first COVID-19 vaccine safe for everyone? More specifically, are mRNA vaccines safe for those with Mast Cell Activation Syndrome (MCAS)? Let’s find out.
How effective are mRNA vaccines?
The mRNA vaccines work by teaching cells to make a specific protein that is designed to trigger an immune response against the COVID-19 virus without having the live virus inside the body. This triggering will cause the production of antibodies, which are unique and specialized immune proteins that target only one pathogen. When the antibodies are created, they remain in the body for future use in case the COVID-19 virus enters the body. This aids in the fight against the virus and can help people avoid grave complications.
According to the World Health Organization (WHO), the Pfizer mRNA vaccine was found to be 95% effective in clinical trials. Many might assume that it being less than 100% of effective is a bad sign; however, even a vaccine with an efficacy of only 50% would effectively control the pandemic.

Can you get the COVID-19 vaccine if you are immunocompromised?
People who are immunocompromised suffer from a weakened immune system. When the body’s defense system is down or not functioning at its best, the ability to fight off infections and diseases such as COVID-19 becomes less efficient. Being immunocompromised can mean that someone is more likely to catch a cold or more likely to get gravely ill from a cold, because there are different degrees of the condition.
Immunocompromisation can be temporary or permanent depending on what is causing it. For example, those who are undergoing cancer treatment may see an improvement in their immune system after recovery, whereas those with congenital diseases may have to live with a compromised immune system for the rest of their lives. Those with less than adequate immune system function may experience worse symptoms or outcomes if they do happen to contract COVID-19.
The good news is that, according to the Centers for Disease Control and Prevention (CDC), immunocompromised people can still become vaccinated against COVID because there is no live virus in the vaccine. The caveat is that those who will be undergoing immunosuppressive therapies should complete the COVID-19 vaccination at least two weeks prior to beginning their therapy, and the vaccine may not be as effective for those with compromised immune systems.
Some people who have been told not to get vaccinated without proper considerations include those with allergies, as some have reported severe allergic reactions to the vaccine, and those who are pregnant, as there have been no clinical trials on the safety of the vaccine in pregnant people.
COVID-19 and mast cell activation disorder
Mast cell activation syndrome (MCAS) occurs when certain cells of the immune system known as mast cells begin to release substances at the wrong time. The substances they release, known as mediator substances, are designed to drive inflammation to help combat infection or heal an injury. When it comes to MCAS and COVID-19, studies show that there may be a link between the viral infection and this cellular dysfunction.
Research has found that mast cells could be contributing factors in the severity or progression of COVID-19, and that it’s possible that the mediators released from mast cells during a COVID-19 infection could cause inflammation that exacerbates the condition. Although more research is needed in this area, studies have found that inhibiting mast cell activity could help to protect a person from a worsened case of the viral infection.

COVID vaccine for MCAS patients
Since the only clear contraindications when it comes to the vaccine are those with allergic reactions and those who are pregnant, it is likely safe for someone with MCAS to take the COVID-19 mRNA vaccines. According to research, those with MCAS have been tolerating the vaccine well so far, and there is no evidence to suggest that having the syndrome renders someone unable to get vaccinated.