Yes, you can still get herpes from a partner who takes daily antiviral medication, but the risk is significantly lower. In the largest study on this question, daily suppressive therapy cut the transmission rate roughly in half, from 3.6% to 1.9% over eight months among couples where one partner had genital herpes and the other did not.
That means medication helps a lot, but it doesn’t eliminate the risk entirely. Here’s what actually happens in your body and your relationship when one partner is on treatment.
How Antiviral Medication Lowers the Risk
Herpes spreads through direct skin-to-skin contact, and it doesn’t require a visible sore. The virus periodically reactivates and travels to the skin’s surface without causing symptoms, a process called asymptomatic shedding. This silent shedding is responsible for a large share of new infections, because neither partner knows the virus is active.
Daily antiviral therapy works by suppressing the virus’s ability to replicate, which means it reaches the skin surface far less often. In one study, people taking daily medication shed the virus on only 1.5% of days without symptoms, compared to 5.1% of days on placebo. That’s a 71% reduction in the days the virus is detectable on the skin. Fewer shedding days translates directly into fewer opportunities for transmission.
What the Numbers Actually Mean for Couples
The landmark trial by Corey and colleagues followed heterosexual couples where one partner had symptomatic genital herpes (HSV-2) and the other did not. Over eight months, 3.6% of partners in the placebo group acquired the virus, compared to 1.9% in the group where the infected partner took daily valacyclovir. That’s a 48% relative reduction in risk.
Those percentages are per couple over an eight-month window, not per sexual encounter. So the per-act risk is quite small, especially with medication on board. But “small” is not zero, and over years of a relationship those individual encounters add up. That’s why the CDC recommends combining suppressive therapy with condom use and avoiding sex during active outbreaks, rather than relying on any single strategy alone.
Why Transmission Still Happens on Medication
Even with consistent daily dosing, the virus is not completely silenced. Breakthrough shedding episodes still occur, just less frequently. During those brief windows, transmission is possible. A few reasons this happens:
- The virus isn’t eliminated. Antiviral medication suppresses replication but doesn’t clear the virus from the nerve cells where it lives permanently. It can reactivate unpredictably.
- Breakthrough outbreaks. Some people still get occasional sores while on daily therapy. Sex during these episodes carries a higher transmission risk than asymptomatic periods.
- Shedding between outbreaks. Even without symptoms, small amounts of virus can appear on the skin for short periods that medication doesn’t catch.
Interestingly, missed doses don’t appear to be a major driver of breakthrough shedding. One study found no meaningful association between the occasional skipped pill and virus appearing on the skin. The vast majority of breakthrough shedding episodes (roughly 87-90% of positive samples) occurred during periods of perfect medication compliance. This suggests the virus simply escapes suppression from time to time regardless of how carefully someone takes their pills.
Combining Strategies for the Lowest Risk
No single method eliminates transmission risk on its own, but layering multiple strategies brings it down substantially. The CDC recommends that couples where one partner has genital herpes consider three approaches together: daily suppressive antiviral therapy, consistent condom use, and skipping sexual contact during active outbreaks.
Condoms on their own reduce herpes transmission by roughly 30-50% in studies, because herpes can affect skin areas a condom doesn’t cover. But combined with daily medication, you’re stacking two partial protections on top of each other. While no large trial has tested all three strategies simultaneously and produced a single combined number, the logic is straightforward: each layer removes a portion of the remaining risk.
HSV-1 vs. HSV-2: Risk Differs by Type
Most of the transmission data comes from studies of genital HSV-2, which is the more common cause of recurring genital herpes. Genital HSV-1 (often acquired through oral sex from a partner with cold sores) behaves differently. It recurs less frequently and sheds on fewer days per year than HSV-2. That means the baseline transmission risk for genital HSV-1 is already lower, and suppressive therapy likely reduces it further, though fewer studies have measured this specifically.
If your partner has genital HSV-1 rather than HSV-2, their risk of passing it to you is lower to begin with, both with and without medication.
Drug Resistance Is Rare
One concern people sometimes have is whether the medication might stop working over time. In people with healthy immune systems, resistance to standard herpes antivirals occurs in fewer than 1% of cases, regardless of how long someone has been on treatment. This means long-term daily use remains effective for the vast majority of people. Resistance is more of a concern for people with significantly weakened immune systems, such as organ transplant recipients.
The Practical Takeaway
If your partner takes daily antiviral medication, your risk of getting herpes is real but low, roughly 2% over eight months in the best available data, and likely lower still if you also use condoms and avoid contact during outbreaks. The medication cuts asymptomatic shedding by about 70% and overall transmission by about half. It works best as one part of a broader approach rather than the sole line of defense. Many couples where one partner has herpes go years without transmitting the virus by combining these strategies consistently.