Preliminary data out of Israel suggests that a fourth dose of either the Pfizer-BioNTech or Moderna Covid vaccine can bring “an increase in antibodies” – more than the increase following a third dose – but still might not be enough to protect against breakthrough infections caused by the Omicron variant (Howard, 2022). Omicron is dominant in many countries – in the United States, for example, CDC data show that the Omicron variant accounts for nearly 100 percent of new Covid cases in the nation (Sullivan, 2022). It can also infect those who are vaccinated or have previously been infected by prior versions of the virus. Early studies, however, show that Omicron is less likely to cause severe illness than the previous delta variant, and that vaccination and a booster still offer strong protection from serious illness, hospitalization, and death (Associated Press, 2022).
In December, Sheba Medical Center in Israel began trialing a fourth dose of vaccines for healthy people ahead of the January rollout of the shot to at-risk individuals, making it “the first study of its kind” (Howard, 2022). The study included more than 270 healthcare workers: 154 received a Pfizer-BioNTech vaccine, 120 received Moderna, and a control group of workers was not given a fourth dose (Federman, 2022). All participants had previously been vaccinated three times with the Pfizer-BioNTech vaccine. Dr. Gili Regev-Yochay, director of the Infection Prevention and Control Unit at Sheba Medical Center, said that while researchers saw an increase in antibodies among those who received fourth doses, the level needed to protect against infection from Omicron “is probably too high for the vaccine, even if it’s a good vaccine” (Howard, 2022). Still, she noted that “slightly fewer” infections were observed among those who got the fourth dose compared to the control group (Howard, 2022).
There’s some debate within the scientific community about the rollout of fourth doses of the vaccine. “We’re in totally uncharted territory for vaccinology,” says Danny Altmann, an immunologist at Imperial College London (Watson, 2022). “We’ve stumbled into a de facto programme of frequent mRNA boosters as an emergency measure, but this really doesn’t feel like the way to go.” Because protection from booster shots might be short-lived, administering endless doses is not a “viable or reasonable long-term global strategy,” says Kanta Subbarao, a virologist at the Peter Doherty Institute for Infection and Immunity in Melbourne, Australia (Watson, 2022). And on January 11, the World Health Organization (WHO) released a statement warning that “a vaccination strategy based on repeated booster doses of the original vaccine composition is unlikely to be appropriate or sustainable” (WHO, 2022).
Some researchers maintain that the answer depends on the desired effect – whether the goal is to reduce severe illness and keep people out of hospitals, or whether boosters are meant to prevent infection and slow virus transmission. Most agree that new vaccines are needed to protect against future variants (Watson, 2022). In the meantime, countries like Denmark, Sweden, Chile, and Cambodia are moving forward with plans to offer fourth doses to specific groups (Saul, 2022; BBC, 2022; Watson, 2022).
References
Associated Press. (2022, January 8). U.K. government advisers recommend against fourth Covid-19 vaccine dose. NBC News. https://www.nbcnews.com/news/world/uk-government-advisers-recommend-fourth-covid-19-vaccine-dose-rcna11466
Covid: Chile starts fourth vaccine dose amid rise in cases. (2022, January 11). BBC News. https://www.bbc.com/news/world-latin-america-59944173
Federman, J. (2022, January 17). Israel study: 4th vaccine shows limited results with omicron. Associated Press. https://apnews.com/article/coronavirus-pandemic-health-middle-east-israel-5da0bbef16209e9c55e48af40248af11
Heller, J., & Lubell, M. (2022, January 4). Fourth COVID-19 vaccine dose boosts antibodies five-fold in Israeli study, PM says. Reuters. https://www.reuters.com/world/middle-east/israeli-study-finds-fourth-dose-covid-19-vaccine-boosts-antibodies-five-fold-pm-2022-01-04/
Howard, J. (2022, January 18). Fourth vaccine dose boosts antibodies, researchers say, but likely not enough to prevent Omicron breakthrough infections. CNN. https://www.cnn.com/2022/01/17/health/israel-fourth-dose-early-data/index.html
Sullivan, K. (2022, January 22). ‘An optimistic trend’: Covid cases are falling, but U.S. isn’t out of the woods yet. NBC News. https://www.nbcnews.com/health/health-news/omicron-wave-covid-cases-finally-peaked-us-rcna13103
Saul, D. (2022, January 12). Denmark First In Europe To Offer 4th Covid Vaccine Dose. Forbes. https://www.forbes.com/sites/dereksaul/2022/01/12/denmark-first-in-europe-to-offer-4th-covid-vaccine-dose/
Watson, C. (2022). Three, four or more: What’s the magic number for booster shots? Nature, 602(7895), 17–18. doi:10.1038/d41586-022-00200-9
World Health Organization. (2022, January 11). Interim Statement on COVID-19 vaccines in the context of the circulation of the Omicron SARS-CoV-2 Variant from the WHO Technical Advisory Group on COVID-19 Vaccine Composition (TAG-CO-VAC). World Health Organization. https://www.who.int/news/item/11-01-2022-interim-statement-on-covid-19-vaccines-in-the-context-of-the-circulation-of-the-omicron-sars-cov-2-variant-from-the-who-technical-advisory-group-on-covid-19-vaccine-composition
