COVID-19 Vaccines Remain Effective Despite Helminth-Induced Immune Modulation, Preclinical Study Shows
Key Insights
A preclinical mouse study found that both mRNA-based (BNT162b2) and protein-based SARS-CoV-2 (search) vaccines maintained protective efficacy despite chronic Schistosoma mansoni (search) infection.
The mRNA vaccine induced strong spike-specific antibody and CD4 T-cell responses comparable to uninfected controls, though multifunctional CD8 T-cell responses were reduced in infected animals.
Vaccinated mice showed markedly reduced viral loads and minimal lung pathology after SARS-CoV-2 (search) challenge, regardless of infection status.
More than a quarter of the world's population is affected by helminth infections, which can profoundly alter the immune system—raising concerns that these parasites might impair vaccine-induced immunity. Now, a preclinical study led by researchers at the German Center for Infection Research (DZIF) (search) and the Technical University of Munich (TUM) (search) provides reassuring evidence: both mRNA- and protein-based SARS-CoV-2 (search) vaccines effectively protected Schistosoma-infected mice against the virus, despite distinct immune response profiles. The findings were published in the journal Frontiers in Immunology.
Helminth infections, including schistosomiasis, are widespread in tropical and subtropical regions, where infectious diseases frequently overlap. Because these parasites influence immune function, the question of whether they might compromise vaccine efficacy carries significant implications for global vaccination strategies.
Study Design and Vaccine Platforms
The German-Swiss research team investigated, in a mouse model, how chronic Schistosoma mansoni (search) infection affects immune responses to two different platforms: the mRNA-based COVID-19 vaccine BNT162b2 (known as Comirnaty) and an alum-adjuvanted recombinant SARS-CoV-2 spike protein (search) vaccine.
Divergent Immune Responses by Platform
The researchers observed clear differences in how the two vaccine platforms stimulated the immune system. The mRNA vaccine induced strong spike-specific antibody responses and CD4 T-cell immunity in Schistosoma-infected mice, which was comparable to that of uninfected controls. Although multifunctional CD8 T-cell responses were reduced in infected animals, overall vaccine-induced immunity remained strong.
The spike protein-based vaccine also elicited robust antibody responses, but generated weaker cellular immune responses than the mRNA vaccine. Nonetheless, immune responses were comparable in infected and non-infected mice.
"Our findings demonstrate that helminth-induced immune modulation changes certain aspects of the vaccine response but does not necessarily reduce protective immunity," said Prof. Dr. Clarissa Prazeres da Costa, a professor of infection and immunity in global health at TUM and a scientist in the DZIF central research theme Neglected Tropical Diseases. "This is encouraging, particularly for regions where parasitic worm infections are highly prevalent."
Protective Efficacy Maintained Against Viral Challenge
To determine whether the altered immune responses affected vaccine performance, the researchers infected vaccinated mice with SARS-CoV-2 (search), utilizing the BSL-3 infrastructure at Helmholtz Munich (search), a state-of-the-art biosafety facility that enables research into airborne pathogens. The results showed that both vaccine platforms effectively protected both infected and non-infected animals. Vaccinated mice showed markedly reduced viral loads and minimal lung pathology after infection, suggesting that protective immunity persisted despite chronic schistosomiasis.
"This study demonstrates that the quality of the immune response varies between vaccine platforms, yet both approaches effectively prevented severe disease in our experimental model," stated DZIF virologist and co-corresponding study author Prof. Ulrike Protzer.
Implications for Global Health
With more than a quarter of the global population living with helminth infections, understanding how these parasites influence vaccination strategies is essential. The new findings suggest that both mRNA- and protein-based vaccines can effectively protect against SARS-CoV-2 (search), even in populations with prevalent helminth infections. However, the researchers note that the study was conducted in a mouse model, and further clinical studies are needed to determine if similar immune mechanisms occur in humans.