AP Photo/Ted S. Warren While lockdown measures have been effective in curbing the spread of the new coronavirus, experts warn that loosening restrictions before a vaccine is available may lead to a resurgence of cases. According to a new study led by researchers at Hong Kong University, there is still a "substantial risk" of new infections, particularly from travelers, and the virus needs to be closely monitored in order to prevent another outbreak. "Although control policies such as physical distancing and behavioral change are likely to be maintained for some time, proactively striking a balance between resuming economic activities and keeping the reproductive number below one is likely to be the best strategy until effective vaccines become widely available," said the study's lead researcher Joseph Wu. Visit Business Insider's homepage for more stories. Lockdown measures have been effective in curbing the "first wave" of the new coronavirus spread, a new study led by researchers at Hong Kong University has found.