Vaccines cause an immune response. There is no evidence that immune responses caused by either vaccines or pathogens weaken the immune system.
A video posted to Facebook from a funeral director in Milton Keynes, U.K., makes numerous false claims about the vaccine rollout. The funeral director claims that he’s seeing a large rise in the number of deaths of heart problems, and he claims this is due to the vaccine. He argues that vaccines cause thrombosis (more commonly known as blood clots) and death.
The funeral director claims that vaccines damage the immune system. This is false. Vaccines provoke an immune response in the same way pathogens do, but without the danger of infection or transmission. Professor Charles Bangham FRS FMedSci, Chair of Immunology at Imperial College London told Full Fact: “While some infectious agents such as HIV can indeed weaken the immune system, there is no evidence that the making of an immune response itself – whether to a vaccine, a pathogen or a toxin - weakens the immune system."
The funeral director claims that COVID-19 vaccines can cause blood clotting. While some of the vaccines have the rare side effect of blood clotting, COVID-19 itself cause severe or even fatal blood clotting at a much higher rate. A hemotologist at the University of Utah, Dr. Yazan Abou-Ismail, was quoted in the university's Health journal saying "Data from the beginning of the pandemic indicated that the incidence of blood clots in severe COVID-19 illness ranged from 20 to 40 percent. The incidence in people with mild or moderate COVID-19 illness was three to nine percent." So while it is entirely possible that the funeral director has seen an increase in the number of people dying with blood clotting events, this has likely been due to the ongoing COVID-19 pandemic, rather than vaccination.
The funeral director also claims that the Omicron variant is a “vaccine injury." Omicron is a variant of concern that was first detected in November in South Africa. As of December 8, there were 437 Omicron cases in the UK. There have not yet been any recorded deaths in the U.K. due to the Omicron variant.
Anti-COVID-vax activists often mislead their audiences by conflating the symptoms of severe COVID-19 with adverse side effects of vaccination. The point of this rhetorical tactic is to spread doubt about the effectiveness of vaccines while still acknowledging the reality that lots of people are falling ill, suffering and dying, and thus not lose credibility. Some of the vaccines, specifically the AstraZeneca and the Johnson & Johnson vaccines, have been reported to have extremely rare side effects that can cause blood clotting, at the rate of a few people per million. However, the Pfizer and Moderna vaccines have not been associated with blood clotting - they can have the rare side effect of myocarditis, or temporary inflammation of the heart. These two side effects often get conflated in anti-vax arguments in order to cast doubt on vaccine safety as a whole. But the rate of serious illness, ongoing medical problems, or death from COVID-19 is far higher than risk of serious adverse effect from vaccines.