How safe is it for vaccinated people to get together? 1. As part of its interim recommendations [these recommendations are not followed anymore], the Centre for Disease Control (CDC) says that people who are fully vaccinated can mix with small groups of other fully vaccinated people indoors without masks or social distancing. The agency also says that the fully vaccinated can meet with unvaccinated people from a single household who are at low risk of developing severe forms of the disease, no masks or distancing required. 2. Still, the decision for vaccinated people to mix involves mental “calculus,” says Swartzberg, which should take into account how likely anyone is to be exposed to the SARS-CoV-2 virus, vaccinated or not, because there is still a small chance even a vaccinated person could become infected or that they could infect an unvaccinated person. 3. As time goes on, when more people are vaccinated and the number of infected individuals continues to drop, Moss says a gathering among vaccinated people “will be a safe one” and will continue to get safer. 4. “To be on the safe side,” says Cynthia Leifer, Associate Professor of Immunology at Cornell University, “we should still practice distancing measures as much as we can in the shorter term until we get broader distribution of the vaccine and greater immunity.” She recommends people to continue to follow the guidelines of avoiding large groups, wearing masks, and staying at least six feet apart. 5. It is also not known how effective the vaccines will be against new variants, including ones that haven’t been discovered yet. 6. “The more that COVID is circulating right now, the more potential there is for variants to arise,” Leifer says. “We can’t predict when a new variant might arise that is perhaps not covered by the vaccine.” 7. The Novavax vaccine, which is not yet approved for use, showed a sizable drop in efficacy - from 49.4 percent - against a variant that originated in South Africa but has since spread internationally. Pfizer and Moderna are still testing how well its vaccines work against a more contagious variant first discovered in the U.K. Question: Pick the option which can be the most suitable synonym for the word 'sizable' used in the passage.

1. respectable
2. extensive
3. substantial
4. whooping