Your questions, answered "Second booster, yes or no? And if yes when?" — Sis in North Carolina "Are there plans for a second booster to be administered?" — Steven in Pennsylvania "Is the CDC recommending another booster shot 5 months after your first booster shot?" — Helene in New Mexico We don't know if health officials will recommend a second booster shot or when that decision might come. Data on the durability of the first round of booster shots is only just beginning to emerge, and much more is needed before we get a better idea. We also have almost no research on how well an additional dose would work against omicron. Scientists simply haven't had enough time to study this. What's clear is that the current boosters provide strong protection against severe disease from this variant. The first real-world data on third-dose effectiveness against omicron came out last week, showing that the shots sharply reduced the risk of hospitalization and death. That's no small victory. As Eric Topol, a public health expert at Scripps Research, put it, boosters "are holding up the wall against severe disease." For now, a key question is how long three-dose protection lasts. Fauci addressed this in an appearance on ABC's "This Week" over the weekend. "We may need to boost again. That's entirely conceivable," he said. "Before we make that decision about yet again another boost, we want to determine clearly what the durability of protection is of that regular boost." A study released today in the New England Journal of Medicine shed some light on the Moderna vaccine's resilience. Researchers found that omicron-fighting antibodies persisted six months after a Moderna booster and remained effective in laboratory tests. But the antibody levels were about six times lower than they were a month after boosting. The decline appeared similar to the decline observed against the delta variant six months after a second vaccine dose, according to one of the study co-authors, David Montefiori of the Duke University School of Medicine. Findings such as those may end up pointing to the need for another booster, Montefiori told me. But scientists first need to see if the drop in antibodies corresponds to an increase in breakthrough infections and hospitalizations, he said. "You still always need the actual clinical data to verify it, and that takes longer," Montefiori said. "The regulatory agencies will wait for those data before making a recommendation." Another recent study looked at third shots of the Pfizer-BioNTech vaccine, finding that antibodies capable of blocking omicron persisted for at least four months after the last dose. Those data suggest a fourth shot may not be needed right away, as my colleague Carolyn Y. Johnson reported this week. Like the Moderna study, the results must be replicated and examined over a longer period. Israel began offering fourth doses to parts of its population in December. But researchers there announced earlier this month that although a fourth shot drove up antibodies, it "only offers a partial defense" against infection. Even if there were clearer evidence supporting the benefits of a fourth dose right now, practical considerations might make health officials reluctant to embrace it. Consider that fewer than two out of three Americans are fully vaccinated. Among them, only about 40 percent have gotten a booster. Given those numbers, a renewed booster campaign for fourth shots may have a minimal impact. Remarking on the possibility of fourth doses earlier this month, CDC Director Rochelle Walensky suggested that officials were focused primarily on convincing the unvaccinated and under-vaccinated to get their shots. "I think our strategy has to be to maximize the protection of the tens of millions of people who continue to be eligible for a third shot before we start thinking about what a fourth shot would look like," she said in a Jan. 7 briefing. "We will be following our own data carefully as well to see how these boosters are working in terms of waning effectiveness, not just for infection, but importantly for severe disease. So more to come as those data emerge." With normal precautions such as masking and social distancing, most boosted people will be well protected against a severe case of covid-19 from omicron, said Montefiori, of Duke. "The fact of matter is most hospitalizations are people who are not vaccinated or are under-vaccinated," he said. Those who haven't gotten the additional dose "need to get boosted as soon as possible," he said. "There's a really big difference in two shots and three shots with omicron." | 
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