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Don’t panic about waning booster protection, say Northwestern experts

Protection against severe illness and hospitalization still holds up

CHICAGO --- How much should we worry about new data released by the Centers for Disease Control showing booster protection wanes after four months? Northwestern Medicine experts say in spite of the decreasing antibodies, the booster still protects well against severe illness and hospitalization, which is the main aim of the vaccines.  

The need and timing for a fourth vaccine dose remains unclear, experts stress.

Here are their comments. For an interview, contact

Dr. Michael Ison is a professor of medicine in infectious diseases at Northwestern University Feinberg School of Medicine.

“The data shows a small decline in the vaccine efficacy versus hospitalization with omicron. With emerging data on a number of fronts, if a fourth dose is needed, it remains unclear at this time if we should be focusing on currently available vaccines, vaccines with different mechanisms of delivery (i.e. nasal vaccines or adjuvanted protein vaccines) or an updated vaccine. Immunocompromised patients already are authorized to get a fourth dose.

“A far bigger problem is that currently only a small fraction of eligible patients have even gotten a third dose/booster. While allowing individuals to get better protection with a fourth dose may be important, increasing the proportion of patients getting a booster (and initial vaccine) is equally, if not more important.”

Dr. Robert Murphy is executive director of the Havey Institute for Global Health at Northwestern University Feinberg School of Medicine.

“The booster will still keep you out of the hospital. That’s the name of the game now. None of these vaccines provide antibodies — which protect you from getting infected — for a very long time against omicron. But the cellular immunity seems to still work well. This is when your sleeper immune cells are activated. The memory immune cells kick in once you get infected and prevent the virus from getting out of control. 

“That’s what protects you from severe disease and keeps you alive. That’s why they say don’t look at infection rates, look at the hospitals to gauge the virus. 

“It will be more difficult to determine when the next booster is really due. We can’t go by antibody levels and cellular immunity is much more difficult to measure.” 

Ramon Lorenzo-Redondo is an assistant professor of medicine in infectious diseases at Northwestern and the bioinformatics director at Northwestern’s Center for Pathogen Genomics and Microbial Evolution.

“The CDC third dose data is based on a small sample of omicron patients, thus, we have to be careful in interpreting the results. This is a very informative study, but the low sample size of participants that received the third dose over four months is still small, and therefore the results can be statistically ‘noisy’ (possibly distorted.)

“The main effect is observed in vaccine efficacy against infection. It appears to be a combination of a degree of waning immunity with time and a capacity of omicron to evade immunity much more efficiently. This is clear when we compare omicron with delta. The decrease in infection prevention was very slight in delta, which goes from 97% for people who recently received the third dose to 89% after over four months for the third dose. 

“Omicron drops from 87% to 66% in four months, but there are only 44 people in that group, so the ‘noise’ is very high and might look different in a larger sample. Even more so for the omicron group after five months, which is only 29 people and shows a 31% vaccine efficacy against infection. The good news is that protection against hospitalization remains high for third dose of mRNA vaccine even during the omicron period. This is the true objective of a vaccine, to prevent hospitalization. 

“I don’t think there is enough data yet to support a fourth dose. It’s dependent on how the pandemic goes. If there is another outbreak of cases, it will become a more important question. Most important is to expand vaccinations and think about alternatives and complimentary measures. There are still a lot of unvaccinated people globally. Vaccination rates in most African countries remain very low. 

“We need a complex approach to COVID-19, where you target as many as mutations as possible. You need something that will protect against omicron variants as well as other variants, particularly those that are closer to the root of the virus so you will have a generalized vaccine.”