Moving the vaccine goalposts: sterilizing immunity was never the rule

Vaccines aren't magical forcefields, but anti-vaxxers keep inventing fake standards so they can claim “failure” of life-saving medicines.

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If you missed it, Maxwell Edison (one of my seven cats) was diagnosed with aggressive large-cell lymphoma on my late brother’s birthday 2 weeks ago. I had goals to catch up on a couple newsletters this week, but then…last week (on my birthday), the veterinary oncologist recommended surgical resection of his intestinal focal mass.

That was based on a study where she and her colleagues found overall median survival for LCL with discrete tumors improved with surgery and chemotherapy versus just chemotherapy alone. Since he is young and overall healthy (besides cancer), he was a good candidate.

Anyway, the surgeon was available the next day, so Maxwell had surgery last week! So instead of managing potential symptoms to a first dose of chemo, I’m now managing surgery of major abdominal surgery for a very stubborn and stir-crazy cat.

The good news: he is doing very well post-op! No anastomosis leaking (a major concern since the margins of the intestine sections were likely partly cancerous) and his incision looks good. His appetite has been amazing; he’s even put on some weight, which means he will be stronger when he starts chemo next week. And he tolerates his shirt (plus looks adorable in it):

My stepdad’s memorial is this coming Sunday and he will be traveling with me up to NY so I can keep an eye on him, but he is pretty much weaned off pain meds at this point too. Keep your fingers crossed that he responds well to chemo for us!

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With that being said, I didn’t have the time I hoped for along with a prep for the memorial. But my latest column in Skeptical Inquirer (Inside Immunity) is now published in digital and print.

It’s especially timely because RFK Jr and his anti-vaccine allies have continued to wage war on vaccines, recycling and reusing the same tactics that have been used for decades to undermine these life-saving medicines. Currently, the lies that circulate target specific vaccine technologies (mRNA as a molecule, for example) as well as the perceived goal of vaccines.

One of the most common? That if a vaccine doesn’t stop all infections it doesn’t work. That’s a lie, of course. But this idea: that vaccines must generate sterilizing immunity is eroding life-saving medical interventions—and harming all of us as a result.

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Sterilizing immunity is the latest anti-vaccine rallying cry.

Sterilizing immunity is a real thing; the problem is that it’s been co-opted by anti-vaccine activists to undermine vaccines. By the current anti-vax logic, if a vaccine doesn’t induce sterilizing immunity—that is, if it doesn’t block all infections—the vaccine is a “failure.” This rhetoric has gained traction since the COVID-19 pandemic, with influencers repeating it on podcasts, blogs, and even the Senate floor. This notion is not just immunologically wrong; it’s a deliberate tactic designed to erode trust in vaccines and harm public health. And it’s working.

Sterilizing immunity is the exception, not the norm

Sterilizing immunity is the holy grail of immune protection against infection: it means that your immune system defenses are so quick, so precise, and so tailored that a virus, bacteria, or other disease-causing microorganism isn’t even able to invade your cells. In other words, your body stops the infection before it even starts. You don’t get infected, you don’t get sick, and you can’t transmit the pathogen to anyone else.

When you get vaccinated (or infected with a pathogen for the first time), your body mounts an immune response. It starts with the innate immune system and leads to the activation of your adaptive immune system and the production of antibodies: proteins that bind specific molecules on a virus (called the antigen) (Bowie and Unterholzner 2008). Some of these antibodies bind to and block the virus from even being able to enter your cells. If the virus can’t enter your cells, it can’t infect and replicate; therefore, the virus is neutralized.

If levels of neutralizing antibodies in your blood or mucosal tissues are high enough when you’re exposed to the virus in the future, they can prevent the virus from taking hold and causing infection outright. That’s sterilizing immunity.

This type of immunity is incredibly rare, because our immune responses and the pathogens it responds to are much more complex than simply [neutralizing antibodies + virus].

Neutralizing antibody levels decline over time, because it’s energy-intensive for your antibody-producing cells (specialized B cells called plasma cells) to continue to make them long term. That decline is normal. Constantly churning out antibodies takes energy, and your body was never meant to do it indefinitely. But you have a lot of other components of your immunity beyond neutralizing antibodies—and that collective response is what protects you from serious illness, even if it doesn’t fully neutralize all viral particles. That’s the science harnessed by vaccines.

After you’re vaccinated, you don’t just make neutralizing antibodies; you also develop immune memory (Pol lard and Bijker 2021). This includes memory B cells and memory T cells. Memory B cells “remember” how to make neutralizing antibodies. If you’re exposed to the same virus in the future, they rapidly activate, turn into plasma cells, and produce fresh batches of neutralizing antibodies in a short period of time.

While B cells are rebuilding anti-body stockpiles, T cells help control the infection from other angles. CD4 (Helper) T cells coordinate the over-all response by helping to activate B cells, communicate between immune cells, and recruit them to assist exposure. Cytotoxic (CD8) T cells target and kill infected cells, limiting the ability of virus to replicate and spread (Sallusto et al. 2004)

While memory immunity may not completely prevent the virus from getting into your body, this coordinate response clears infection faster, limiting the spread of a virus. This reduces viral load, which means you are often less likely to infect others. It also means less severe illness and shorter duration when you’re sick. That’s why vaccination matters. That’s why vaccinated people have milder illness and are less likely to develop complications, require hospitalization, or die even if they get infected.

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Most vaccines don’t generate sterilizing immunity, and no one has pretended they do

The goal of vaccination isn’t to automatically stop a pathogen at the gate; it’s to train your immune system to limit damage from a pathogen by developing that memory immunity. That means individuals and the collective society experience less illness, fewer complications, and improved overall health. Vaccines don’t need to elicit sterilizing immunity to be incredibly effective. In fact, most vaccines do not provide sterilizing immunity. If you live in the United States in 2025, you’ve benefited from non-sterilizing vaccines.

Let’s look at some examples:

The tetanus vaccine is a toxoid vaccine, because the symptoms of tetanus are not due to the bacterium Clostridium tetani itself but rather a toxin it produces. The vaccine doesn’t prevent infection from the bacteria. It neutralizes the toxin, tetanospasmin, that causes muscle paralysis and death. Routine tetanus vaccination (including adult boosters) has nearly eliminated tetanus in the United States. The roughly thirty cases a year now are almost entirely in unvaccinated people. The bacterium is still ubiquitous in the environment. The vaccine prevents potentially fatal illness from that likely exposure.

The Hib vaccine protects against Haemophilus influenzae B, a bacterial infection that is the leading cause of life-threatening illnesses in children under five, including meningitis, pneumonia, and epiglottitis. It induces a very strong memory immune response but not sterilizing immunity (Gilsdorf 2021). Before the vaccine was available, Hib led to 20,000 invasive infections (severe disease progression) and 1,000 deaths in children under five in the United States every year. Today Hib incidence has been reduced by 99 percent solely due to vaccines.

The hepatitis B vaccine protects against the hepatitis B virus (HBV), transmitted through bodily fluids, including perinatally (around the time of birth), unsafe medical practices, sexual activity, and other person-to-person fluid exchange. Hepatitis B infection causes acute and chronic illness because hepatitis B virus is a DNA virus that can persist in liver cells indefinitely. Children infected have a 90 percent risk of developing chronic hepatitis, which leads to liver damage, cirrhosis, and liver cancer. Fifty-eight percent of all liver cancers are due to hepatitis B (Institute of Medicine 2010).

We protect against this now with a three-dose vaccine, starting at birth, to protect a newborn against that potential perinatal transmission when they are at high risk. This vaccine does not induce sterilizing immunity, but it does protect against illness, infection, and cancer. The Hepatitis B vaccine has reduced the global prevalence of chronic hepatitis B in children under five from about 5 percent in the 1980s to less than 1 percent today. Vaccination programs have reduced new infections among kids by over 95 percent in areas with high vaccine uptake.

(more on HBV vaccine below):

Newborn hepatitis B vaccines save lives, prevent cancer, and don't cause autism

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Seasonal flu vaccines have to contend with the influenza viruses that mutate incredibly quickly thanks to their segmented genome, which makes sterilizing immunity a pipe dream. Still, flu vaccines have an incredible public health impact. They are 40–60 percent effective at preventing symptomatic illness; they reduce hospitalizations by roughly 50 percent and risk of ICU admission by 80 percent (Rondy et al. 2017; Thompson et al. 2018). In the United States, that means they prevent 7.5 million illnesses, 2–6 million medical visits, 40,000–120,000 hospitalizations, and 3,000–12,000 deaths every year. Flu vaccines reduce risk of death among children by 75 percent, prevent poor pregnancy outcomes such as preterm birth or stillbirth, and are associated with a 15–20 percent reduction in all-cause mortality primarily from cardiac and respiratory complications (Walzer et al. 2020, Olson et al. 2022, Chaves et al. 2023).

(more on flu vaccines below):

Everyone 6 months and older should get a flu shot every year

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I could go on, but I think you get the idea. None of these vaccines are “sterilizing,” but all of them save lives. They’re designed by scientific experts with biological reality in mind. That they don’t prevent 100 percent of infections does not remotely mean they’re “failures,” but that rhetoric has been propagated by disinformation peddlers to erode trust in these life-changing medicines.

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Vaccines are not magical forcefields

Vaccines are one of the most impactful developments of modern medicine, but they aren’t magical forcefields. This all-or-nothing attitude doesn’t exist for anything else, so why do we let it control discourse about vaccines?

Chemotherapies and immunotherapies don’t guarantee cancer remission, but they dramatically improve odds and increase survival rates. Would you say “You got cancer again, so chemo didn’t work” to someone whose cancer came back after ten years in remission?

Blood pressure medications don’t prevent every stroke or heart attack, but they reduce the risk and occurrence of them dramatically.

Antibiotics don’t eliminate every bacterial infection, but we acknowledge they’ve saved millions of lives—and we still use them, responsibly.

Seatbelts don’t prevent car crashes; they prevent you from flying through the windshield if a crash occurs, reducing the likelihood of death and the severity of injuries.

Umbrellas don’t prevent you from getting wet in all cases, but they prevent you from being drenched in a thunderstorm, which means they did their job.

Vaccines are no different; just like seatbelts, airbags, and other medications, they are risk mitigation measures that we know are effective. But we also know they’re not always effective. Vaccines must be viewed in the same way.

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‘Sterilizing immunity’ is a dog whistle used by anti-vaccine activists

Vaccines are not intended to make people invincible. They’re designed to give you tools to be resilient when faced with an infectious agent. And guess what? By every credible measurement, they do that. The perception that vaccines must be 100 percent effective or they are not effective at all has been deliberately fueled by the rhetoric of Robert F. Kennedy Jr., Joseph Mercola, Del Bigtree, Peter McCullough, and many others who are destroying our health agencies from within.

Their sterilizing immunity narrative is part of a decades-long strategy to erode public health and trust in science. They demand perfection through biologically implausible expectations such as “vaccines should stop all infections.” Then, with this ridiculous bar for science, they’ll paint incredible success as failure (yes, the millions upon millions of lives saved with COVID-19 vaccines to them is a failure). And finally, they’ll profit by selling that distrust through book deals, donations to their activist organizations, podcast agreements, and more.

This isn’t holding science to a high standard; it’s undermining public trust by design. Trust in science has eroded because the public has been convinced by these people, people with zero relevant expertise, to misunderstand data. We cannot let influencers co-opt scientific facts. It harms us as individuals and as a society.

Vaccines aren’t broken. Our collective understanding of immunology is. And it’s thanks to the very people who profit by spreading lies about vaccines. Vaccines prevent illness, reduce suffering, and save lives. That’s true even if they don’t prevent every infection. The next time someone says, “But I still got sick,” ask them:

Did you survive? Were you hospitalized? Did your infection end in days instead of weeks?

If so, congratulations! That’s not vaccine failure; that’s success. You lived. Science worked.

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Now, more than ever, we all must join in the fight for science.

Thank you for supporting evidence-based science communication. With outbreaks of preventable diseases, refusal of evidence-based medical interventions, propagation of pseudoscience by prominent public “personalities”, it’s needed now more than ever.

More science education, less disinformation.

- Andrea

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ImmunoLogic is written by Dr. Andrea Love, PhD - immunologist and microbiologist. She works full-time in life sciences biotech and has had a lifelong passion for closing the science literacy gap and combating pseudoscience and health misinformation as far back as her childhood. This newsletter and her science communication on her social media pages are born from that passion. Follow on Instagram, Threads, Twitter, and Facebook, or support the newsletter by subscribing below: