How Long Will A Vaccine Make It Safe For You To Travel?

Vaccines approved so far in the United States have been highly effective not just against preventing symptomatic infection but more importantly against severe Covid leading to hospitalization and death, and also – we are learning – against asymptomatic infection which means vaccination cuts down on spread of the disease. We just do not know how long this protection lasts because not enough time has passed yet to make this determination. And that’s a problem for policymakers as they consider whether to open up travel without testing or quarantine to those who have been vaccinated.

This is a problem with the idea of a vaccine passport, that we do not know how such a document should be valid for, since we do not know how long conferred protection lasts. Conventional wisdom is that we’ll need booster shots, and studies are progressing now to determine when, however it’s also likely that protection will last for some time albeit waning over time.

The CDC says, “We don’t know how long protection lasts for those who are vaccinated.”

We do know that natural immunity lasts quite some time for most people who have been infected, beyond when they show antibodies. While there’s concern about re-infection from the South African and Brazilian strains of the virus, and there’s some evidence for this, documented reinfections remain limited even as the virus has changed and there’s little indication (yet) that reinfections tend to be as or more serious compared to original infections. Approved vaccines against Covid-19 generate greater anitbody responses to the virus than are found in recovered patients.

Ultimately we don’t know how long protection against Covid-19 from vaccines will last, because there hasn’t been enough time that’s passed to tell us. It was just one year ago today that the first dose of the Moderna vaccine was given to a patient in a clinical trial, for instance.

In other words, we can’t really know how if protection lasts a year until a year has passed. We can’t know if protection lasts two years until two years have passed. What we can do is test immune response over time and if it declines we can project that out and make educated guesses.

The Points Guy answered the question about how long protection lasts but I don’t think the metric they offer is correct since it won’t merely be a function of antibody levels in those who have been vaccinated,

“We currently do not know, as we are living through the experiment,” said Dr. Jenny Yu, the senior manager of medical integrity at Healthline (which is owned by Red Ventures, as is The Points Guy). “As time passes with the first group of people having received the vaccines as part of the clinical trial, their antibody levels will inform us how long this immunity will last.”

In order to determine how long protection lasts, we’ll need:

  • Tracking vaccinated individuals over a period of time to see when their immunity wanes. We’ll no longer have a placebo group to compare against but can make statistical comparisons against more recent vaccinations, against those who have chosen not to get vaccinated, and against earlier periods.

  • Testing immune response in the blood of vaccinated individuals over time. Contra The Points Guy it’s not drawing blood and testing for antibodies that will tell us how long immune response lasts, but rather exposing drawn blood to SARS-CoV-2 and watching immune response – antibodies may wane without the virus present but looking only at antibodies misses the role of t-cells in response to virus exposure as well as memory B-cells.

  • Larger data sets than those who participated in the first trial since different people have different immune reactions. The first Moderna trial gave different doses to 45 young, healthy adults. That doesn’t tell us how long protection lasts across a variety of age groups and physical conditions even now a year later.

There are now human challenge trials moving forward in the U.K. and that would be another way of testing continued efficacy – exposing vaccinated people to the virus after a period of time to see whether they continue to have an immune response. We’d likely need more fool-proof treatments before the medical establishment considered this ethical here for this purpose.

It’s the uncertainty that makes policymaking here difficult. While The Points Guy also noted that,

New York State announced earlier this week that it would ease entry and quarantine requirements for those who have been fully vaccinated against COVID-19. Now, domestic travelers no longer have to quarantine if they’ve been vaccinated within 90 days.

However this is no longer fully accurate. This change was made two weeks ago (March 3, not this week) and subsequently the state declared that domestic travelers will not have to quarantine at all starting April 1 whether vaccinated or not.

Nonetheless New York’s initial plan to require quarantine for arriving passengers who had been vaccinated after 90 days reflected the uncertainty surrounding duration of protection. We know that it lasts more than 3 months and are continuing to see data on just how much more.

About Gary Leff

Gary Leff is one of the foremost experts in the field of miles, points, and frequent business travel - a topic he has covered since 2002. Co-founder of frequent flyer community, emcee of the Freddie Awards, and named one of the "World's Top Travel Experts" by Conde' Nast Traveler (2010-Present) Gary has been a guest on most major news media, profiled in several top print publications, and published broadly on the topic of consumer loyalty. More About Gary »

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  1. A reasonable discussion. Unfortunately not everyone realizes that scientists don’t have all the answers–it’s like Fauci changing his position on masks. Theories evolve, discoveries are made, and new data changes what is understood. Also, a lot of science is based on probabilities–we can’t know everything so if something is highly likely that is what is used. (Somebody, somewhere might be totally immune to the virus, but policy has to be made on the vast majority of humans being susceptible.) Unfortunately though a lot of folks don’t understand statistics and how it works. All this may make science less credible to many members of the public, though it should be the reverse. Those in the field are willing to learn and revise what they think they know with new knowledge. The result will be theories and practices that are at least very close to what is happening, but like knowing how long vaccines last they take time and a lot of study to develop.

  2. Jason sounds like the third grade bully that ends up out of work, fixing cars, and attending the occasional klans rally

  3. The standard American school curriculum is woefully inadequate to prepare the average person for understanding statistics let alone immunology and other basic sciences. Add to that the fact that nuance has been dead for at least the last decade and anything over 140 characters is not worth reading nowadays and you get our current predicament.

    Gary – I must congratulate you. This is probably the most detailed and scientifically valid thing you’ve said all year on this topic. There are more factors in vaccine responses that T or B cells though but for brevity I think your article was great.

  4. There will always be some level of risk. Even the pfizer/moderna vaccines have an efficacy rate of 95% (not 100%).

  5. @Joey – 95% refers to efficacy against symptomatic covid, but we don’t care if you get symptoms (well we do, but only a little). We care whether you get severe covid, wind up in a hospital, etc. We don’t want to overwhelm hospitals and we don’t want people to, we want them to recover.

    There’s still risk sure but there’s background risk across daily lives, every time you get into a car there’s risk. So far the vaccines appear to reduce Covid risk to manageable levels.

  6. Scientists are still talking theory while US and UK case and death counts are falling far faster than projected. There is no data on a pandemic that can be tracked the way covid19 has been tracked but scientists have sounded alarm bells far louder and more dire than turned out to be the case on a number of occasions.

    The CDC also said that samples of donated blood shows that about 25% of Americans have natural antibodies to covid – which has tripled over the past six months.

    Combined with the vaccinated population, the number of covid exposed, non-vaccinated Americans is probably going to push the US into herd immunity within a couple months, not much later this year as some would have us believe.

    Countries like the EU and Brazil which are not vaccinating will take much longer because the population that has natural immunity (survived covid) and those getting the vaccine are largely different populations. The elderly and most vulnerable to covid are largely not blood donors.

    The great thing about the CDC and scientists talking about covid so much is that the general public is getting the data – and there are people that will demand a return to normal even if the conclusions of the data are different than what the “experts” claim.

    the covid vaccine effort is the largest in human history – to parallel the rate of covid infections. Given that all viruses reach a point where they lose their ability to kill wide segments of the population naturally, covid would have reached that point. Vaccination has rapidly accelerated it.

    Large portions of the world are reopening or will do so as soon as they see the value of vaccination – that is happening in the EU and Brazil even as they struggle through yet more lockdowns.

    Talking about global travel starting again in the 3rd quarter of 2021 is reasonable for countries that take vaccination seriously and want to reopen.

    Taking booster shots might or might not be necessary – but many diseases require follow-up vaccinations so the concept is not new to humanity. The key is getting back to normal using a combination of disease- induced immunity and vaccination.

  7. So far only drrichard, gary, and Tim have made intelligent, cogent comments. All of the other depressed nasty trolling commenters need to go to their favoirite far left or far right (depending on your preference) web site and commiserate with your kindred folk about how messed up everything is! Get a Life!

  8. “We currently do not know.” …..Know what else we don’t know?…..We don’t know if you’ll be killed by a meteorite crashing though your living room ceiling tomorrow afternoon. Let’s just wait 20 years just in case. In the mean time, don’t forget to wear 3 masks. Also, there will be a $35,000 fine and 3 years jail time for asking flight attendants for a second bottle of water.

  9. @ CHRIS – are you one of the people that doesn’t want to wear a mask because they don’t see a risk? Or one of the people who doesn’t want to take a vaccine because it’s too risky?

  10. @ John. I’m fully vaccinated.
    I wear a mask just to play along with this stupidity….for now.

  11. I’ve heard Pfizer designed the vaccine so that you need to get re-vaccinated every 2 weeks.
    That’s how they are covering their 4% dividend

  12. The 90-day thing that New York is talking about is from the CDC and it is absurd. If vaccines don’t protect for more than 90 days, we all give up, because you’ll never get the whole world vaccinated four times a year, and my great grandchildren, who haven’t been born yet, will become eligible for Social Security before the mask mandates and social distancing end. I’m exaggerating, but the standard should be, if you’re vaccinated you’re OK until there is evidence that shows otherwise. It has been about 8 months since the large trials began. We are still reporting for periodic blood draws. and will be doing so for about 25 months in all. It should not be that hard to notice when immunity starts to decrease (if it does), both from analyzing blood samples and from actual experience (if it happens) of vaccinated people becoming symptomatic. In the meantime, we already know the vaccine is good for way more than 90 days, so any policy that uses that standard is another example of underselling and under-rewarding vaccination.

  13. Now do:
    How Long Will the influenza Vaccine Make It Safe For You To Travel?
    How Long Will A Measles Vaccine Make It Safe For You To Travel?
    How Long Will a chicken pox Vaccine Make It Safe For You To Travel?
    How Long Will A mumps Vaccine Make It Safe For You To Travel?
    How Long Will A shingles Vaccine Make It Safe For You To Travel?
    How Long Will A pneumonia Vaccine Make It Safe For You To Travel?

  14. There is NO proven evidence that Covid vaccinations are “highly effective.” There is much evidence that people THINK they’re effective which, in the short term, may be good enough to get you admitted into a foreign country. Right now, sadly, the evidence (incredibly) is that you are more likely after your first shot to GET Covid! Nobody wants to believe this, however, so it’s simply ignored. Our best hope is that this virus keeps going away naturally, and then we won’t have to deal with vaccination efficacy. In the meantime. it’s probably better to pretend that everything is great with the vaxes because, otherwise, we’re left with the crazy amount of irrational Covid fear.

  15. As Gary said, there are a lot of unknowns, but the general consensus in the immunology community in terms of protection against the South African variant is that 1. prior infection gives you partial immunity, which is probably in the 0~50% range, but does NOT protect against severe disease, and 2. most of the reasonably effective vaccines also give you partial protection, probably in the 45~70% range (except for AstraZeneca, which gives you almost none), but they DO protect you mostly against severe disease.

    That said, there is a much stronger consensus in the immunology community: vaccinated people “returning to normal” (traveling, going to restaurants, etc) amidst a partially vaccinated population will lead to higher chances of the worst variants spreading, or the virus evolving into even worse immunity-evading variants, and is quite likely to actually delay the reopening of our society even further. This is the message that almost every reputable immunologist gives in interviews with reputable media outlets, and the message that this blog conveniently ignores. The safe time to travel is clear: “when you’re vaccinated yourself, and when most OTHER people are vaccinated at your origin AND destination.”

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