The COVID vaccine has been a hot topic on this forum. Both myself and my co-moderator @pricewool have already received both doses of the COVID vaccine. I received Pfizer and Price received the Moderna version, both of us has minimal side effects from the vaccine and also receive IVIG like you.
It’s a personal decision, but the MDA (muscular dystrophy association) has recommended that ANY patients with neuromuscular disorders including LEMS receive the COVID vaccine.
You can check out the article and answers to frequently asked questions here.
Both my neurologist and rheumatologist recommended I receive the vaccine because LEMS patients are at high risk to develop serious complications from COVID-19.
I posted a review of my experience with receiving the COVID vaccine and you can check that out as well. Price also posted a review of his experience and you can see it here.
We also posted a topic that includes other members of the forum with LEMS experience with the COVID Vaccine
Hope this helps!