“Next to clean water, no single intervention has had so profound an effect on reducing mortality from childhood diseases as has the widespread introduction of vaccines,” says the National Academy of Sciences. Yet outbreaks of measles and mumps in recent years reflect a rise in public hesitancy and skepticism toward immunization. Amid today’s pandemic, as many eagerly await a vaccine against the novel coronavirus, SARS-CoV-2, here are five myths about this medical innovation.

Myth No. 1: Vaccines are cash cows for the pharmaceutical industry.

The anti-vaccine community often claims that vaccines are incredibly lucrative. In 2019, anti-vaccination activist Del Bigtree released a video entitled “Vaccines: Big Pharma’s Cash Cow” full of ominous music that pointed out how vaccine profits increased by 1,100% in the past 20 years. Children’s Health Defense, an anti-vaccination organization, recently criticized the government for “prioritizing” potential coronavirus vaccines over “existing therapeutics” that “do not offer comparable financial windfalls.”

But the costs to develop a vaccine are often higher than for a therapeutic. The clinical trials to test vaccines’ safety and effectiveness tend to be larger, and last longer, than trials for conventional medicines. And vaccines generally do not command high prices: When a vaccine to prevent human papillomavirus (HPV) was introduced in 2006, its $360 price tag provoked outrage around the world. Today, it costs $570. In contrast, a flu shot costs $30, a tetanus shot (along with diphtheria and pertussis protection) runs $45 and the measles-mump-rubella vaccine costs $76. Moreover, the vaccine market makes up only 2% to 3% of the worldwide pharmaceutical industry, according to the Atlantic.

For pharmaceutical companies that now routinely produce medicines with price tags of tens or hundreds of thousands of dollars, comparatively low-priced, low-margin vaccines often don’t seem worth the effort. Our studies at Washington University in St. Louis revealed that by 2000, the Food and Drug Administration had approved vaccines to shield Americans from 26 different pathogens (two target the same virus and one was withdrawn). Two decades later, we can protect against just one additional pathogen: HPV.

Myth No. 2: Vaccines are full of toxic heavy metals.

The most prominent proponent of this theory, Robert F. Kennedy Jr., claimed in a notorious article co-published by Rolling Stone and Salon in 2005 that vaccines with thimerosal (a preservative containing trace amounts of mercury) could be linked to “the epidemic of childhood neurological disorders.”In 2015, anti-vaccine activist Jenny McCarthy called aluminum the “other devil,” asserting that vaccines contained even higher levels of that metal.

The purported link between vaccines, thimerosal and autism has been repeatedly debunked — and according to the FDA, only a few, rarely used influenza vaccines still contain the preservative. Aluminum, meanwhile, is abundant throughout our environment but is not heavily present in vaccines; it is not generally considered a heavy metal. According to the Children’s Hospital of Philadelphia, the amount of aluminum in the vaccines babies get in their first six months is just over half as much as the amount ingested during six months of breast-feeding and a 10th of what is imbibed by formula-fed babies. The FDA has repeatedly verified that aluminum adjuvants (which help create a stronger immune response) are safe and effective.

Myth No. 3: A covid 19 vaccine will arrive in 12 to 18 months.

“Potential coronavirus vaccine being tested in Germany could ‘supply millions’ by end of year,” a CNN headline proclaimed this past week. “If you mean one [vaccine] that can be used in a mass vaccination campaign, allowing us all to get on with our lives, then 12 to 18 months is probably right,” Marian Wentworth, president and chief executive of Management Sciences for Health, told the Guardian.

But history reveals that even with comparable public visibility and impatience, developing a vaccine almost always takes far longer. Jonas Salk, was working on the polio vaccine when he received a grant from the March of Dimes in 1951 and announced positive results in 1953. Large-scale trials began in 1954 — a rushed process that culminated in the vaccine’s approval for use in 1955. “Vaccine development is a long, complex process, often lasting 10-15 years and involving a combination of public and private involvement,” according to the College of Physicians of Philadelphia.

That process includes assessments to ensure that a vaccine elicits an immune response and the gathering of laboratory and real-world evidence that this immunity will prevent disease. Most important, it also includes long-term evaluation of whether the vaccine causes unexpected damage. These activities require time, and improved technology does not accelerate them. Rushing these procedures — and there will certainly be pressure to do so — escalates the risk of an ineffective or dangerous vaccine. Indeed, the Salk vaccine for polio was rushed, and improper manufacturing led to unnecessary deaths.

Myth No. 4: Once a vaccine exists, covid-19 will no longer be a problem.

“Things won’t go back to truly normal until we have a vaccine that we’ve gotten out to basically the entire world,” Bill Gates said in early April. According to Axios, “The world is pinning its hopes on a vaccine for covid-19 to save lives, return to normal and emerge from an economic recession.”

But it’s unclear whether prior infections with the novel coronavirus or a vaccine would confer durable protection. Work on related coronaviruses, such as SARS and the Middle East respiratory syndrome virus, suggest that some protective immunity might be generated by vaccine candidates or natural exposure, but the length of protection remains uncertain: One Oxford University study suggests that protection may last only two or three years.

Vaccination can eliminate some diseases in the wild, such as smallpox and polio, because only humans harbor these viruses. It is unclear whether animals and humans can give SARS-CoV-2 back to one another, but there have been reports of lions, tigers, dogs and house cats infected with the virus, and many other species, including fruit bats and ferrets, may harbor it as well.

Myth No. 5: Herd immunity will soon protect you from covid-19.

During protests in April against social distancing orders in Michigan, one woman told an NBC affiliate that she doubted the wisdom of “so-called scientists” and that she believes “very strongly in herd immunity.” Similarly, Dan Erickson, a doctor who appeared on Fox News, told host Laura Ingraham, “I think the key is the vaccine helps get you to herd immunity, but also, you can get to herd immunity without a vaccine.”

A problem with herd immunity is that the share of people who must be protected against infection varies from pathogen to pathogen. Protection from smallpox requires that 95% of individuals be able to resist the disease, whereas 85% should be resistant to polio. Measles requires 80% protection for herd immunity, which explains outbreaks in areas that have experienced even marginal increases in anti-vaccine sentiment. An even greater fraction of the population must be immunized against some pathogens, since certain people (e.g., the elderly, cancer survivors and other immune-suppressed individuals) may be susceptible to infection even if they received a prior immunization. Consequently, immune-suppressed individuals should be counted among the nonimmunized. We don’t yet know the threshold of protection that will be protect against SARS-CoV-2, butbut what it certain is that the virus is highly transmissible between people and has the potential to create asymptomatic “super-spreaders,” who could unknowingly begin anew waves of new infection. Consequently, we need to push on all fronts to deploy safe and effective medicines in the short term (within the next year) and vaccines over a longer time frame (perhaps two-to-ten years). In the meantime, we must acclimate to a chronic new consisting of social distancing and assisting the heroic work of disease-tracking epidemiologists, who will, by the end of summer, be confronted by both influenza and the inevitable return of SARS CoV2.

Michael S. Kinch is an associate vice chancellor at Washington University in St. Louis and leads the Centers for Research Innovation in Biotechnology and Drug Discovery. He is also the author of “Between Hope and Fear,” a history of vaccines.