Yes, it is both safe and highly advisable to get a tetanus-diphtheria (Td or DT) vaccine now. Having recovered from chickenpox 21 days ago, your body has had ample time to recover, and your immune system can safely handle the vaccine. Tetanus vaccines are inactivated (not live), so they will not cause a relapse or interact with your previous illness. Preventing tetanus after a cut is critical, especially if your last booster was more than 5 to 10 years ago. Please have a healthcare provider evaluate your wound, clean it thoroughly, and administer the vaccine as soon as possible.