Health Wanted: COVID-19, Five Years Later

March 14, 2025
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HEALTH WANTED, a weekly radio show and podcast produced in partnership with WABE, brings need-to-know public health headlines and breaks down the science behind trending topics.

The Episode

The topic: Five years ago this week, the World Health Organization declared COVID-19 a pandemic. This fast-tracked information sharing, vaccine development and deployment, and activated the global scientific community as they worked to understand the virus and minimize its spread. This week on Health Wanted, host Laurel Bristow and guest Akiko Iwasaki, PhD, co-lead investigator of the Yale COVID-19 Recovery Study, look back at the COVID-19 pandemic and discuss what we’ve learned, where we are, and what lies ahead.

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The takeaway: In the past five years, the COVID-19 pandemic has taught us many lessons about how we should handle future disease outbreaks, especially in terms of communicating with the public at different stages.

  • Throughout the pandemic, public health officials often struggled to communicate important information about COVID-19 effectively, especially as our understanding evolved. This led to confusion and mistrust in information about masking, social distancing, stay-at-home orders, and more.
  • Like information, COVID-19 treatments also evolved over the course of the pandemic. For example, Paxlovid is an antiviral that showed promise in its ability to slow disease progression and shorten symptoms, but newer data shows it is most effective in unvaccinated people over 60. Misinformation circulated about the medications hydroxychloroquine and ivermectin being effective treatments for COVID-19, which they are not.
  • The COVID-19 vaccine made it through development in under one year because of years of prior mRNA research and a level of public will and volunteerism that let it move through the clinical trial process rapidly. It is estimated that the vaccine prevented 20 million deaths globally in its first year on the market. Despite this, skepticism remains about the vaccine, its effectiveness and safety, and vaccine mandates, in part due to flaws in how we communicated about the vaccine.

 

The Interview

The guest: Akiko Iwasaki, PhD

The key takeaways:

  • For a portion of the population, the symptoms of COVID-19 can persist for months after the acute infection ends, resulting in what we now call “long COVID.” This can happen even when you only have mild COVID symptoms and is more common in women and middle-aged individuals.
  • We have several hypotheses to explain long COVID:
    • Persistent infection: People may continue to be infected with the SARS-CoV-2 virus for months or years after initial symptoms clear up.
    • Autoimmunity: Many viruses can trigger autoimmune conditions, and this may be the underlying cause of some long COVID cases.
    • Chronic inflammation: Long-term inflammation and tissue damage not being properly repaired may be leading to the cognitive impairment that many people with long COVID face.
    • Latent virus activation: Many adults carry a herpes virus in its latent, inactive form. Some patients with long COVID have had these viruses reactivated by a COVID infection.
  • The type of treatment that will benefit someone with long COVID depends on the underlying cause of their ongoing symptoms. Researchers are working on identifying biomarkers that will show the cause so they can test targeted treatments in clinical trials.

 

The Listener Questions 

Can ivermectin treat cancer?

Ivermectin is a phenomenal antiparasitic. It has been revolutionary in our ability to treat many neglected tropical diseases like river blindness, scabies, and as an off-label treatment for rosacea. Its effectiveness at treating other things has less evidence to support it.

The reason ivermectin is so good as an antiparasitic is that we know how it works—it paralyzes parasites, and they die. But this is not translatable to something like cancer or COVID-19.

In the case of COVID-19, studies done in humans show no benefits to using ivermectin.

For cancer, all of the evidence of a benefit is in cell lines, and not in actual clinical trials with humans. So, you can be hopeful but you can’t claim this is evidence that ivermectin will be a cure for cancer before you’ve tried it in human clinical trials.

Does exposure to parasites lower your chance of developing allergies?

A constant quandary in health is what accounts for the rise in allergies in high income countries. Is it air pollution? Is it diet? Is it that we live “cleaner” lives and aren’t exposed to as many pathogens that used to kill us but have now been replaced with asthma and dust mite allergies?

This is called the “hygiene hypothesis,” and basically it’s the idea that our reduced exposure to dirt means that we are more likely to experience allergies, asthma, eczema, and hay fever.

The theory goes that there are two types of helper T cells in your immune system, very creatively called TH1 and TH2. When you get a parasitic infection, TH1 gets called to action to drive your immune response, but when it’s active it has a second job of basically telling TH2 cells to chill out.

This is important because TH2 cells stimulate the production of IgE antibodies, which are the antibodies that react to common allergens, like dust mites, and stimulate your response like itching and sneezing. So, if you don’t have stimulation of these TH1 cells earlier in life (through exposure to bacteria or parasites), then your TH2 can just go crazy causing allergies.

There’s some data to suggest that infection with soil helminths (worm parasites that live in the dirt like hookworm) are associated with lower risk of asthma, but this is not a good strategy for allergy prevention for many reasons:

  • One, because untreated parasitic infections have their own problems.
  • Two, because some kinds of soil helminths, like ascaris, can migrate to your lungs which is going to make you cough.
  • Three, because there are other factors that contribute to allergies like diet and sedentary lifestyle.

 

Catch all the listener questions and Laurel’s answers on the full episode of Health Wanted by:  

 

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