The quest to find a definitive cure for Alzheimer’s disease has encountered yet another setback. But here's where it gets controversial: recent attempts to repurpose antiviral drugs used against herpes infections have not only failed but also produced unexpected worse outcomes.
This week, researchers at Columbia University published their findings from a carefully controlled trial that left many puzzled. In this study, individuals diagnosed with early Alzheimer’s or cognitive impairment who also tested positive for herpes simplex virus antibodies were given an antiviral medication—valacyclovir (better known by the brand name Valtrex)—for 18 months. The goal was to see if targeting the herpes virus could slow or reverse the progression of Alzheimer’s.
To everyone’s surprise, the group receiving the antiviral treatment did not experience any benefits. Instead, their cognitive abilities deteriorated more rapidly than those on a placebo. Brain scans confirmed that the medication did not improve markers of brain health or prevent neurodegeneration. As the researchers noted in their publication in JAMA, “Valacyclovir was not effective; in fact, cognitive decline was worse among those who took it.”
And this is the part most people miss: while these results seem discouraging, they don’t necessarily disprove the idea that viruses could be involved in Alzheimer’s. It’s important to understand that Alzheimer’s is characterized by the buildup of amyloid beta and tau proteins in the brain—molecular hallmarks that scientists are still trying to fully understand. Some recent studies have suggested that certain viral infections might contribute to or exacerbate this process, leading to the so-called viral hypothesis of Alzheimer’s. For instance, experiments in mice have shown that herpesvirus infections can trigger amyloid buildup, and autopsy studies of Alzheimer’s patients sometimes find herpesviruses lurking in brain tissue.
However, so far, evidence linking herpes viruses directly to Alzheimer’s remains largely indirect. But if viruses are a contributing factor, then logically, eradicating or controlling these infections early in life might help prevent or slow down the disease. That was precisely what researchers hoped to test with this trial.
This was a bold attempt, but unfortunately, it underscores a critical point: treating herpes infections in people who already have early symptoms of Alzheimer’s doesn’t seem to help—and might even worsen outcomes. It raises the question of whether intervention needs to happen much earlier, perhaps decades before symptoms emerge, much like how some researchers are now investigating whether anti-amyloid drugs can prevent Alzheimer’s in genetically predisposed individuals before clinical signs appear.
Yet, there’s an alternative strategy that holds promise—vaccination. Studies have started to reveal that vaccines against certain herpesviruses, like the shingles vaccine (which targets varicella-zoster virus, a herpesvirus responsible for shingles), could potentially lower the risk of developing dementia later in life. While this connection isn’t yet fully proven, these findings suggest a hopeful avenue: could vaccines be a simple, public health tool in our fight against Alzheimer’s?
As David Knopman, a neurologist at the Mayo Clinic, mentioned in an editorial accompanying the study, “Might there be a role for vaccination at the population level? Maybe.” But he also emphasizes that more research is essential to establish whether preventing herpes reactivation through vaccines could indeed reduce Alzheimer’s risk.
So, the big question remains: does infection control through vaccination truly offer a protective benefit against Alzheimer’s? Or is the viral hypothesis just another unproven theory? We invite you to share your thoughts below. Do you believe that targeting viruses could someday become part of the standard approach to preventing or treating Alzheimer’s, or is this a case of wishful thinking? The conversation continues—what’s your take?**
