Messaging from the CDC and health departments throughout the pandemic have consistently underscored the importance of avoiding travel due to the very nature of travel increasing exposure to others, in turn increasing one’s risk of becoming infected, having an adverse health outcome, and also increasing the risk of spreading COVID-19 to others both during and for some time after returning.
In the context of rising numbers of diagnosed cases, hospitalizations, deaths, and overwhelmed healthcare systems, the argument to refrain from unnecessary travel had been clear. But as we see the fall in case numbers, the data on effectiveness of interventions such as masks and distancing, the distribution of highly effective vaccines, and the economic and psychological impact of lockdowns, the hope and desire to relax travel restrictions is becoming more apparent.
Indeed, on Dec. 27, 2020, nearly 1.3 million people boarded airplanes in the U.S., the highest number since last March, according to the TSA.
The fire hose of new information continues to inundate the medical, scientific, and public health communities. It is often hard to stay updated on all the latest studies that could inform major decisions and policies.
Even when presented with the same information, expert opinions on what is “safe” and what is “ethical” regarding issues such as dining, schools, mass gatherings, and travel are as nuanced as the projections of what the pandemic will look like in the coming months.
Let’s look at what the data reveals on some of the key factors that come into play.
Vaccination
Little argument can be made against the astonishing efficacy of COVID-19 vaccines in protecting individuals against illness and death. According to the phase III clinical trials, Pfizer’s COVID-19 vaccine reduced the risk of getting ill from COVID-19 by 95%, Moderna’s by 94.5%, Johnson & Johnson’s by 66%, and AstraZeneca’s by approximately 70%.
Other vaccines coming down the pipeline have reported similar rates of protection. Data is also coming out regarding the level of protection after just the first dose of vaccine for those that require two doses.
In the U.K., the Public Health England found that one dose of the Pfizer vaccine reduced the risk of infection among healthcare workers under 65 years old by 72% at 3 weeks. Based on this data, many experts advocate for a national strategy that includes postponing the second dose of vaccine in order to more widely distribute first doses across the country (and globe) sooner, particularly as the concern about variants arise.
While these efficacy rates are encouraging for the individual who is vaccinated, the less understood but important variable in deciding the safety and ethics of travel goes beyond the individual’s protection and on to how effective vaccines are in preventing a person from transmitting COVID-19 to others.
We are just starting to see promising signals to be able to answer this question. Several studies have documented the effect some vaccines have had in reducing the viral load among those who have had breakthrough infections. In addition, Israel’s Ministry of Health reported in mid-February that Pfizer’s vaccine was shown to be 89% effective at preventing infection of any kind and 94% effective against symptomatic infection in a population where more than 27% of people in the country over age 15 had been fully vaccinated.
Further data is needed to truly understand just how much reduction in transmission is offered by vaccines, but the medical community is very optimistic that the amount of reduction will be impressive and considerable.
How protective these vaccines are and will be against emerging variants is also still largely unknown. Given the error-prone nature of the replication machinery of SARS-CoV-2, as well as its capacity to mutate under immune pressure, as spread continues so does the chance that more variants will arise.
Probably the most well-known variant, B.1.1.7, first described in the U.K. in the fall of 2020, was found to be the predominant strain in the study by Israel’s Ministry of Health, accounting for more than 81% of COVID-19 test samples.
Therefore, the high level of vaccine efficacy against both illness and transmission can be applied to that specific variant. Vaccine manufacturers are studying how well vaccines perform against all variants of concern in the laboratory setting as well.
While the level of neutralizing antibody against some variants has been shown to be reduced, many agree that there is likely still considerable protection in the real world given the baseline high level of efficacy and the additional role that T and B cells play in immunity, which is not easily measured in the laboratory.
Other variants of concern are circulating worldwide, including ones that have increased transmissibility, potential to cause more severe illness, death, and reduced efficacy to the currently available vaccines. In response to this, the FDA has stated that modifications to previously authorized vaccines may be authorized without the need for further lengthy clinical trials.
Herd Immunity
While we don’t fully know when “herd immunity” will be reached, most estimate this to be when 70%-80% of the population is considered immune.
With the rate of re-infection within 90 days of recovery from COVID-19 being so low, the CDC does not recommend quarantine for exposures within that timeframe. And given the data known so far, the CDC also does not recommend quarantine after an exposure for those who have been fully vaccinated and have had time to develop full protection (i.e., more than 2 weeks from their second dose).
So, for a traveler who is immune either by being fully vaccinated or having recently recovered from COVID-19, herd immunity at a given destination and within their home community is less of a variable, both in terms of risk of illness and risk of transmitting virus to others. Add on behavioral methods proven to substantially reduce one’s risk and viral transmission (fitted masks, social distancing, outdoors over indoors, etc.) and one can feel good about traveling responsibly.
For the non-immune person, the level of community spread, and the presence of herd immunity are more critical questions. And for couples, families, and groups traveling together, the level of safety is only as good as the weakest link.
Conversely, herd immunity in the home community of a non-immune traveler is a factor that would impact the level of risk that the traveler poses to the people during the travel and at the destination. Several groups have estimated current immunity in the United States, with most estimating this to be at approximately 30%-40% of the population as of February.
It is hard to predict when herd immunity will be reached in the U.S., though experts and models predict sometime between spring and summer 2021 depending on the deployment and acceptance of vaccines. But getting to that threshold will undoubtedly help policymakers in lifting many of the testing requirements and quarantine restrictions.
Location
The CDC monitors case counts of COVID-19 around the globe closely and has developed a four-level system, which aligns with the U.S. Department of State’s travel advisory system.
Countries or territories determined to be Level 1 have low levels of COVID-19, and usual precautions are advised. Those in Level 4 have very high levels of COVID-19, and travelers are advised to avoid travel to these destinations.
These levels can and do change rapidly, so for those who choose to travel, I recommend that they stay connected with the Smart Traveler Enrollment Program, a free service run by the State Department.
One caveat to note: Your home country or travel destination may be a Level 1 or 2, but it is possible that you may be sharing your flight, vehicle, airport terminals, and other common spaces with others coming from a community with a higher level of transmission. This also applies to destinations with higher concentrations of tourists coming from around the globe.
So if you enjoy time away, it is still important to practice the precautions known to mitigate risk.
Countries with higher vaccination rates and more robust healthcare infrastructures, such as Canada and those in Western Europe, are likely to reach herd immunity sooner than other places with lower vaccination rates. This may influence your decision, particularly if you are not fully vaccinated by the time you leave.
In addition, it is probably easier to find a facility with COVID testing that would meet the current requirement for re-entry back into the United States.
Countries with exceptionally low rates of COVID-19 (New Zealand, Vietnam, China, etc.) are currently deemed safer to travel to than countries with higher rates of transmission. Many of these countries have historically implemented earlier and more aggressive lockdowns, so you may want to have a contingency plan in the event of a new lockdown if cases rise during your stay.
Exposure-notification apps can be an additional convenience, particularly if they are integrated with facilities that are able to provide timely testing, if needed. Regardless of whether this is available, I recommend familiarizing yourself with the local medical facilities available if you get sick and as well as the testing resources available at your destination before your departure, so you have a plan to be able to return home.
Where Does That Leave Us Today?
Just as we have been doing for the past year, we need to continually weigh the individual and population-level health risks along with the economic impacts of international travel with great care and humility. Public health messaging has continuing to stress the need for the public to take the utmost precautions, and with good reason as the number of deaths in the U.S. has now surpassed 500,000.
But, if you have been vaccinated, know that you are much less of a risk to those around you and you are more safely able to spend time traveling and visiting loved ones. This is especially true if those loved ones have also been vaccinated.
Until vaccines become more widely available to the broader population, however, it does remain important to continue to prevent the spread of COVID-19 with measures well proven to bring down transmission. We are seeing signals that we will get closer to normal soon.
Every day is one day closer to the end of this pandemic. And when the wait is finally over, the gates of travel will open in ways we have never seen before.
Joyce Sanchez, MD, is an infectious disease specialist and travel health clinic medical director at the Medical College of Wisconsin in Milwaukee.