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No evidence for COVID-19 booster vaccines yet

Still unknown if boosters will increase disease prevention, send vaccines instead to unvaccinated nations, medical experts say

CHICAGO --- Not so fast on COVID-19 vaccine boosters, say Northwestern Medicine experts after the Food and Drug Administration announced plans Friday to speed efforts to authorize extra doses of the coronavirus vaccines for Americans with weakened immune systems. 

Northwestern infectious disease experts cited lack of evidence a booster will make a significant clinical difference in preventing infection. Rather, the push should be to provide vaccines to the unvaccinated around the world to eliminate the global pandemic.

Here are the experts in ethics and infectious diseases:

Seema Shah is Founders' Board Professor of Medical Ethics, associate professor of pediatrics at Northwestern University Feinberg School of Medicine and the Pritzker School of Law at Northwestern.

Dr. Michael Angarone is associate professor of medicine in infectious diseases at Northwestern.

Dr. Sadiya Khan is assistant professor of preventive medicine in epidemiology at Northwestern. 

Dr. Michael Angarone 

“There is data that immune-compromised individuals have a less robust response to the SARS-CoV2 vaccines, which is not unexpected since they also have lower response rates to all vaccines. But there is a lack of evidence that giving a third or fourth dose enhances the immune response dramatically. The study out of Johns Hopkins shows an increase in antibody response in about 30% of those that received a third dose, still not a 100% response. And we also do not know what this antibody response means. Are these neutralizing (protective) antibodies at high titers, low titers and what is the correct titer?

“There is a decrease in efficacy in the vaccine. At six months when looking at non-delta variant there is a small drop from more than 95% to about 90%. When looking at the delta variant, the efficacy decrease is more profound with a drop to 75 to 80% with the Pfizer vaccine. A study from Israel puts the drop in efficacy from 90% to 40%. The biggest issue is the context of this drop and how to interpret it. Also, there seems to still be protection from severe and critical disease. 

“At some point we will need a booster or a repeat vaccination with new variants, but we need more data. We should focus our efforts on vaccinating as many people as possible in the United States and around the world before we start giving booster doses of vaccine.”

Dr. Sadiya Khan 

“We are also used to boosters for other vaccines or having annual influenza vaccines. However, whether multiple doses or different dosages are better than one or two depending on the vaccine is not known. We need to address that question with certainty and confidence and focus on the highest risk folks first, those who have received organ transplants. 

“We have no clear evidence a booster will prevent infection in those who are immune compromised or what degree of immune compromise is needed to warrant a booster. Those over age 65 may have a lower titer or response to the vaccine, but that doesn’t mean it isn’t effective at doing what it needs to do if someone is exposed. While there is data on a third dose improving titers, we still do not have evidence on the clinical significance in different people with varying levels of immune compromised states in preventing disease and not just lab values.

“If we only focus on high-income countries, even if there is a benefit, the marginal benefit of ‘boosters’ is not going to be as large as dealing with the bigger problem of a global pandemic. Treating only people in one country will never end the pandemic. We need to focus on eliminating the virus from the population at large from a public health perspective.”

Seema Shah on booster ethics

“If there is good evidence that some groups are not adequately protected by the authorized dose of vaccines, there are no new ethical concerns raised by using boosters in those groups. Choosing to use boosters in groups who have insufficient protection, rather than sending the vaccines elsewhere, is on par with choosing to prioritize vaccination of most of the U.S. population in the first place. Without good evidence of a need for boosters, however, it is wasteful and unfair not to share our supply with other countries in dire straits.

“The average person should not be getting an ‘off-label’ booster when there are people who really need the vaccines. We don’t yet know whether it’s even worthwhile for healthy, younger people who have been vaccinated.”