How long should I wait between two different vaccines?

Last reviewed: 2026-06-14

Quick answer

It depends on which two vaccines. The general rule: between two inactivated vaccines (which contain no live pathogen — e.g. inactivated flu, pneumococcal, COVID-19) there's no minimum interval, so they can be given on the same day or at any spacing. Between a live vaccine and an inactivated one there's also no required gap. But for two injectable live (attenuated) vaccines, if they're not given on the same day, the general advice is to space them by at least four weeks (28 days). This is just the broad rule — follow your doctor's advice for the specific vaccines you're getting.

"After one jab, how long before I can have another?" There's no single answer — it depends on which two vaccines. Here's the broad rule of thumb.

Inactivated + inactivated: no required gap

Inactivated and recombinant vaccines contain no live pathogen (e.g. inactivated flu, pneumococcal, COVID-19, hepatitis B). Between two of these there's no minimum interval — they can be given on the same day (at different sites) or at any spacing, without affecting each other's protection.

Live + inactivated: no required gap

Between a live vaccine and an inactivated one there's likewise no required gap — same day or any time.

Live + live (injectable): at least four weeks apart

If you're getting two injectable live (attenuated) vaccines and not on the same day, the general advice is to space them by at least four weeks (28 days). The reason: the first live vaccine may briefly affect the body's response to the second. If they're given on the same day, this doesn't apply.

The key points

Most common adult vaccines (flu, pneumococcal, COVID-19) are inactivated, with no required gap between them.
The four-week interval really only matters for two injectable live vaccines together — relatively uncommon in adult vaccination.
The above is the broad rule. Individual product information may carry specific advice, so follow your doctor's guidance for the exact vaccines you're getting.

Before the jab, tell your doctor what you've had recently and what you plan to have, and let them set the best timing for you.

Answer six short questions to see which vaccines are worth discussing with your GP, and why.

Based on your age, health, and travel plans, using HK Department of Health and CDC guidance. A ranked list of vaccines, with the reason each one applies to you.

Rule-based

The recommendations follow HK Department of Health and US CDC guidance, and you can see how each one was reached.

Private

Your answers stay on your own device. We never receive or store them.

Explained

Every recommendation comes with the reason it applies to you.

Start the recommender →