Alum, an aluminum-based adjuvant or immune-enhancer used in many vaccines — including inactivated-virus COVID-19 vaccines — helps protect against the targeted (homologous) virus strain.
However, alum may raise infection risk from new (heterologous) virus strains, referred to as “breakthrough” infections, according to a preprint study published on Research Square.
Of the 13.5 billion COVID-19 vaccine doses administered globally, 5 billion used inactivated coronavirus as their active ingredient. Unlike the Pfizer and Moderna vaccines, inactivated-virus COVID-19 vaccines do not use mRNA. Instead, they use killed or weakened viruses to bring about the immune response.
Examples of virus-inactivated COVID-19 vaccines include China’s CoronaVac product, which was distributed in 40 countries, and the Indian COVAXIN product.
Alum also increases the risk for vaccine-associated enhanced respiratory disease (VAERD), a potentially life-threatening complication, after infection with a new strain. However, this effect disappears when alum is replaced by a different adjuvant, according to the study.
Researchers exposed vaccinated mice to two different virus strains
Researchers led by Mark Heise, Ph.D., an immunologist at the University of North Carolina, used laboratory mice to compare the effectiveness of an inactivated, alum-containing SARS-CoV-2 vaccine (iCoV2) against two coronaviruses: the strain for which the vaccine was designed, known as the homologous strain, and a previously unencountered (“heterologous”) coronavirus.
The test animals were bred specifically for susceptibility to coronavirus-induced lung disease.
The alum-containing vaccine protected against homologous (i.e., same virus) challenges with no apparent ill effects.
But when the mice were exposed to a coronavirus that the vaccine was not designed to protect against, they developed classic symptoms of VAERD. The symptoms included delayed coronavirus clearance and decreased lung function.
This effect, which persisted for at least 10 months, appears to be related to the adjuvant because when alum was replaced with Ribi — an unapproved, research-only adjuvant — mice cleared the virus faster and did not develop VAERD.
Alum’s effect on VAERD was partially reduced by re-immunizing the animals with a Ribi-based adjuvant vaccine…
Children's Health Defense 
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