Spring break is upon us as and despite the CDC’s non-essential travel warning, thousands of students and families are still traveling across the country. More than a million passengers have traveled through US airports daily for at least 11 days in a row, according to data from the TSA, breaking a record for travel during the pandemic. Many have flocked to Florida, with the state’s complete lack of Covid-19 restrictions a tempting respite for some. As spring break travelers return home to different corners of the U.S. they could accelerate the spread of the variants, prompting a potential national surge unless states cease relaxing Covid-19 restrictions
Let’s begin by looking at last year, Florida Governor Ron Desantis famously minimized the impact of spring break parties, neglecting the fact that as spring break travelers returned home they seeded the virus across the country. As infections eventually spread nationwide, Florida experienced its own surge in the summer and over winter (Figure 1). As public health officials have repeatedly cautioned throughout the pandemic, none of our population is safe from infection until the entire population is safe. If you look at the case rates in the table below (Figure 2) you will see how national cases rose dramatically after Spring break last year.
This year the infectious conditions for Spring break are even more potent with the introduction of several highly transmissible variants. Daily US case rates are sitting at approximately 55,000 compared to the few hundreds from last year. The B.1.1.7 variant now represents more than half of Florida’s cases and could be even higher since fewer than 1% of Covid-19 cases are tested in Florida to detect the mutations. The chances of exposure at the Spring break parties are high with zero Covid-19 mitigation measures in place and Police officers finding that they have no avenue to enforce safe behavior with the rollback of mandates. Returning travelers will also be seeding these variants in states that have relaxed restrictions, leaving them even more vulnerable.
To see what can happen in the U.S. let’s look at the current wave of infections engulfing Europe fueled by the more contagious variants. The B.1.1.7 variant is rapidly spreading across 27 European countries and is now dominant in Denmark, Italy, Ireland, Germany, France, the Netherlands, Spain, and Portugal. New daily cases in Italy have surged from a weekly average of just over 12,000 in January to more than 22,000 this week as a result of new variants. In Germany, 7,485 new infections and 250 deaths were reported over a 24-hour period this week.
Even without the impact of Spring break, cases in some states such as Michigan and Connecticut have begun to rise and cases in other states like New York have plateaued at a disturbing high level. Approximately 15 states have more cases than they did two weeks ago, and about 19 states have higher test positivity rates than two weeks ago, which points to higher rates of infection.
Michigan recorded nearly 17,000 new cases last week, resulting in a 300% increase from the same week last month (Figure 3). The state’s positivity rate recently hit 9%, the highest increase since mid-January. In Connecticut, there has been an average of 944 cases per day for the last week, an increase of 32 percent from the average two weeks earlier (Figure 4).
It is still too early to rely on vaccinations alone to protect us from this potential surge. Only 13.7% of the total U.S. population has been fully vaccinated and these will take two weeks to take effect. The UK’s success in dramatically reducing cases has been a combination of mass vaccinations and stringent public measures including travel bans and strict lockdowns. Israel’s relative success in reopening after a strong vaccination campaign is also due to a strong contract tracing system and the use of QR codes to keep track of those who are vaccinated. But Israel is still threatened by the very high infection in neighboring countries Jordan (Figure 5) and Lebanon.
The efficacy of the current vaccines against the variants and the complete duration of immune protection is still largely uncharted territory and we must as always err on the side of caution. A recent preprint study used predictive modeling techniques to estimate the strength and length of immune protection conferred by seven different vaccines over time. The results suggest that the more protective a vaccine is immediately following immunization, the longer protection will last. This means the Pfizer vaccine, for example, would only take about six months for the vaccine to drop to a level of only 50% protection and the J&J vaccine would take just two months to drop to such low levels. If this prediction is correct we will need to retool our vaccine strategies so they better address the issue of waning immunity against Covid-19 and do not leave vaccines vulnerable.
This should not deter anyone from accepting any vaccine when available, all vaccines still protect recipients from death and hospitalization caused by Covid-19. It is simply a reminder that despite the glimmer of hope vaccines provide, we are far from the end of the pandemic and with the rapidly spreading variants now is the time to be doubling down on restrictions not relaxing them.