I will be traveling to Costa Rica and Chile over the next 6-12 months and spending 1-2 months in each country while I am there.

I checked the CDC website for Costa Rica and Chile, as well as the general vaccination guidelines page, and it recommends that I get vaccinated for Hepatitis A and B and Typhoid 3-4 weeks before I travel.

Is it necessary to wait, or can I get these vaccinations done now so that I have one more thing out of the way? Are travel vaccinations like "routine" vaccinations in that you just need to keep up on them every year or so, or do you really need to take them closer to when you travel?

2 Answers 2


The advice to get vaccinated 3-4 weeks prior to traveling should be read as "at least 3-4 weeks prior". Typically, it takes your body's immune system a little while to respond to the vaccine by creating antibodies. Thus, if you travel immediately after getting a vaccination, you may still be vulnerable to those infections.

In the case of hepatitis vaccine the protection it affords will last 10 years. So getting it a bit sooner than 4 weeks prior to travel is a non-issue. I've never heard of a traveler-oriented vaccine that doesn't afford at least 3 years protection.

So, in summary, if it is more convenient to get your vaccinations 6 months prior to travel, then go right ahead. Just keep track of the duration of their effectiveness for future travels. You'll need to 'top them up' sooner then otherwise as a consequence.

  • Also, more time between vaccination and travel gives you better options on vaccine schedules. Many are best spread out across multiple doses, with usually several weeks between doses, and if rushed in fewer or faster doses have increased risks of side effects or reduced effectiveness. Commented Sep 12, 2019 at 10:07

Hep A vaccine is generally given as two shots at 0- and 6- months. Hep B vaccine is generally given as three shots, at 0-, 1-, and 6-months. The A/B combo vaccine Twinrix also follow the same schedule as the Hep B vaccine. You aren't fully covered for the normal vaccine duration unless you complete the schedule.

(There are accelerated dosage schedules if you have a real need for the vaccines, like working in a high risk area, but these are the normal schedules.)

So, you really have two options:

  1. Start the series more than 6 months before your travels, and have it all done in advance.
  2. Start the series at least one month before your travels, so you at least get the first and second Hep B shots.
  • 7
    This is not entirely accurate. Getting the first Hep A shot will give you about 10 years of protection. Getting the follow-up shot, 6-12 months later, extends this to 21-27 years. As for the Hep B, it is not nearly as easy to contract it as Hep A and is generally only considered 'necessary' for travelers planning to stay a long time (over 6 months) or are considered 'at-risk' (likely to encounter blood, e.g. health professionals). The three dose shot you mention will however give lifetime protection so it is worth getting if you travel frequently to areas at risk for Hep B.
    – Kris
    Commented Apr 10, 2012 at 15:52
  • @Kris, thanks for the additional detail. I wasn't aware the first Hep A shot gave such long protection since I missed my second shot and the doctor advised me that I needed to start over... clearly no urgency on that one! Commented Apr 10, 2012 at 15:54

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