Why experts say monoclonal antibodies aren't vaccine substitute

Despite more than 187 million Americans being fully vaccinated against COVID-19 and data and attestations from researchers and public health officials that the vaccines are safe an effective, a small and in some cases vocal minority of Americans are reluctant to get the shot.

The reasons vary, but a number of those people are instead turning to treatments after they are diagnosed that have far less evidence to support their safety and effectiveness, including monoclonal antibodies -- a trend that experts say is worrying.

Currently, over 1 million doses of monoclonal antibody infusions have been given in the United States. Use of monoclonal antibodies gained steam during the delta variant surge over the summer when Florida and other states opened clinics to administer the drugs in an attempt to keep sick people out of overwhelmed hospitals.

Monoclonal antibodies have been authorized for post-exposure prophylaxis, meaning they are used shortly after someone tests positive in order to prevent progression to severe disease. The antibodies range in effectiveness depending on type, but some have been shown in to reduce COVID-related hospitalization or death by up to 85%.

COVID-19 vaccines have been tested in large clinical trials with hundreds of thousands of people. The CDC says over 215 million people have safely received at least one dose of a COVID-19 vaccine, including 187 million who have been fully vaccinated, either with the one-dose Johnson & Johnson shot, or two dose mRNA vaccines.

All three COVID-19 vaccines have gone through the most intensive safety monitoring in U.S. history by government agencies, fully independent safety monitoring boards, vaccine manufacturers and academic researchers. The Pfizer COVID vaccine is currently FDA authorized for people 12 and older. The Moderna and Johnson & Johnson vaccines are authorized for those 18 and up.

Common side effects of the COVID-19 vaccine include pain or swelling at the injection site. Fever, muscle aches, chills, fatigue or headaches can also occur but should go away within a few days. More serious health problems, such as unusual heart rhythm or blood clots, are exceedingly rare -- and in fact, are more likely to happen to an unvaccinated person who becomes sick with COVID-19 than with the vaccine itself.

'More concerned with treatment rather than prevention'

Many vaccine holdouts in the U.S. have cited the vaccines' emergency use authorization status -- a special FDA pathway helps accelerate the often-slow regulatory process during a national emergency. Pfizer's vaccine is now fully FDA approved for people 16 and older, while Moderna and Johnson & Johnson are still under emergency authorization, awaiting approval.

However, some experts interviewed by ABC news say some patients who won't get vaccinated also ask for monoclonal antibody treatment after the are diagnosed with COVID, which has the same emergency use authorization. Doctors say they are perplexed about why some people pursue monoclonal antibody treatment which is supposed to reduce the risk of hospitalization in high-risk vulnerable people instead of prevention.

“People are more concerned with treatment rather than prevention," said Rupali Limaye, Ph.D., the director of behavioral and implementation science for the International Vaccine Access Center at Johns Hopkins School of Public Health.

"When they are in the hospital and needing COVID treatment, their options are limited -- but they know they need treatment to fight COVID. Decision-making is very different related to preventative behaviors,” said Limaye.

What to know about monoclonal antibodies

The FDA has granted emergency authorization status to four antibody treatments for COVID-19. These antibody treatments are most helpful in mild to moderate disease. Not all antibody treatments are equally effective, and some have lost their potency in the face of new COVID-19 variants.

According to the FDA, monoclonal antibodies are laboratory-made proteins designed to mimic the immune system’s ability to fight disease particles known as antigens. For example, sotrovimab is a monoclonal antibody that prevents COVID-19 infection by blocking the virus' spike protein.

The data supporting these antibodies is much more limited than the extensive data supporting currently approved and authorized vaccines.

“Monoclonal antibodies are an important treatment option for high-risk patients. However, the idea that they can be used as a prevention tool is severely misguided," said Dr. Andrew Pavia, Infectious Diseases Society of America fellow, NIH COVID treatment guidelines panel member and chief of pediatric infectious diseases at the University of Utah School of Medicine.

"They are no substitute for cheap and effective prevention tools like masks and vaccines,” said Pavia.

Other COVID treatments under EUA include tocilizumab, a monoclonal antibody that is not directed toward the virus but instead reduces inflammation in already hospitalized patients. Remdesivir, an anti-viral, is FDA approved for hospitalized patients over 12 but under EUA for kids less than 12.

All of these treatments require an infusion and a trip to a medical center. Now, pharmaceutical companies are also working on easy-to-prescribe pills that can ease symptoms for people who are already sick, but doctors stress these are also not a replacement for a vaccine that can help prevent disease in the first place.

Ways to boost vaccination

Doctors interviewed by ABC News say their patients want an easy solution that will protect them from COVID-19. For most, that's a vaccine. For others, misinformation surrounding vaccines can stand in the way, prompting them to seek alternatives.

“Hesitancy falls on a continuum. That means that those that are hesitant may refuse some vaccines, may accept vaccines but be unsure about the decision or may have concerns. There are validated scales that measure attitudes related to safety, efficacy, past vaccine behavior and vaccine intentions.” said Limaye.

The CDC suggests providers ask vaccine-hesitant patients a scaled question, for example, “On a scale of 1 to 10, how likely are you to get the COVID vaccine? (1 = never and 10 = vaccine appointment is already set)." The goal is to help patients become more aware and move toward higher numbers on the scale.

For example, if a patient says that they are a three on the scale, providers can ask why and why not a lower number? This helps patients to reiterate the benefit of vaccines instead of explaining why they have not gotten it. Providers can then further follow up by asking, “What would help to go to a four or a five?”

While there are many successful ways to talk to people about the COVID vaccine -- all methods center around a common theme of empathy, curiosity and open communication to help end the pandemic.

ABC News' Sony Salzman contributed to this report.

Jess Dawson, M.D., a Master of Public Health candidate at Johns Hopkins Bloomberg School of Public Health, is a contributor to the ABC News Medical Unit.