Summary:  Covid 19 vaccination is recommended for all eligible children and adults with vascular anomalies.  The risk of developing a Covid 19 infection when unvaccinated greatly outweighs the known risks of vaccination.

Vascular malformations and risk of thrombosis with vaccination.

Some people are concerned about whether there may be an increased risk in having a Covid 19 vaccination if they have a vascular malformation, because of an increased risk of clot formation.  While there is a very small risk of developing blood clots after Covid19 vaccination, this is related to the immune response to the vaccine and is different from the way clots form in a vascular malformation.  People who already have conditions where thrombosis occurs, such as vascular malformations, are not thought to be at higher risk than others for the rare clots in the brain which have been described with Astrazenica vaccine in particular.  Infection with Covid19, on the other hand, does involve a high risk of developing blood clots, and although there have been no published reports of major problems with vascular malformations in Covid infection, this remains a theoretical concern.  Since prior vaccination has been proven to reduce the severity of Covid19 infection, we believe that this makes it more, not less important that people with vascular malformations get vaccinated before they are exposed to the virus. 

Can Covid vaccination cause increased symptoms in a vascular malformation?

When the body is infected with a virus, the immune system mounts a highly effective response to eliminate the virus and restore health, but if the immune system has never encountered the virus before, it takes about a week or more to identify the virus as a threat.  The Covid virus seems to be particularly good at exploiting this delay to spread widely in the body, so that by the time the immune system is ready to react, the virus can be found all over the body.  It is the immune system’s reaction to this large load of virus which causes most of the symptoms of Covid infection, including blood clot formation.  Vaccination is a process of presenting a small section of protein from the virus to the immune system which learns to recognise it as foreign.  When someone who has been previously vaccinated is infected by Covid, their immune system recognises the virus protein and begins its response almost immediately, before the virus has become widely spread.  Infection may not be prevented, but the symptoms, including thrombosis, are much less.  Because vaccination stimulates the immune system to respond to the protein, vaccination itself is sometimes followed by some symptoms similar to those experienced in Covid infection.  There have been a few reports of people with vascular malformations having some increased pain in the days after vaccination, but this increase only lasts a short while and is most likely due to the immune system learning to respond to the protein.  The reduced risk of much worse symptoms which can follow an actual infection is a strong justification for getting vaccinated before being exposed to the virus.

Should I have a Covid vaccine if I am on Sirolimus?

Sirolimus (rapamycin) can be a very effective treatment for low-flow vascular malformations, but we know that it can have some suppressive effect on the immune system.  There is concern, but no proof, that sirolimus may reduce the body’s ability to fight off a viral infection like Covid.  For this reason Sirolimus treatment may be ceased if someone becomes infected with Covid.  On the other hand, the data to date in patients on Sirolimus for renal transplants developing Covid, hasn’t shown worse disease in those that remained on it compared to those that had it ceased, and there are even some new reports suggesting that Sirolimus may be useful for those with Covid infection (this data is preliminary and not yet substantiated). If you are on sirolimus and at risk of being infected with Covid, which one can assume will be nearly everyone either now or in the near future, then you should discuss with your treating doctor the risks and benefits of continuing sirolimus treatment.

Successful vaccination relies on the body’s immune response to the protein in the vaccine, and we know that in patients who are on full immune suppression, such as those with organ transplants, vaccination is not as effective as it is in people who’s immune system is not suppressed.  We do not know how much the effectiveness of vaccination will be reduced with milder forms of immune suppression as can be experienced with sirolimus treatment, but it is theoretically possible that the vaccine may not work quite as well.  On the other hand, there is no increased risk to vaccination while on sirolimus, and a greater need for the protection vaccination may provide, so there is no reason not to proceed to vaccination.  You should discuss with your treating doctor before booking your vaccine appointment whether stopping sirolimus for a few days prior to the vaccination might make it more effective.