The holiday season can be intense. People are traveling, hosting family and friends, and going to events — all the while keeping up other responsibilities of work and caregiving.

All this activity has me thinking about the importance of keeping our immune systems healthy. What are some habits that everyone should adopt, such as getting good sleep, eating well and exercising regularly? Conversely, are there some habits people should consider stopping because of their negative impacts on the immune system?

What about vaccines — is it too late to get vaccinated against respiratory viruses if you are going to family gatherings with newborns or older adults? And are there other safety tips people should keep in mind to reduce their chances of getting sick during the holidays?

To help sort through these questions, I spoke with CNN wellness expert Dr. Leana Wen. Wen is an emergency physician and clinical associate professor at George Washington University. She previously was Baltimore’s health commissioner.

CNN: Why it is especially important to keep our immune system healthy?

Dr. Leana Wen: Our immune systems are our body’s natural defense against viruses, bacteria and other potential pathogens. Strong, healthy immune systems reduce the risk of contracting infectious diseases and falling seriously ill from them. The immune system is also implicated in some chronic diseases.

Immunity is influenced by many factors, some of which are within our control. Getting recommended vaccines, for example, helps to build immunity against certain diseases. Beyond vaccines, there are several lifestyle factors that research shows also boost our body’s immune function.

CNN: What habits should people adopt if they want to boost their immune function?

Wen: There are three important habits that people should consider. First, keep physically active. In addition to reducing your chance of developing chronic diseases like diabetes, cancer and heart disease, exercise stimulates the immune system. Being physically active may lower your chance of dying from the flu or pneumonia, according to the US Centers for Disease Control and Prevention.

Second, cut down on ultraprocessed foods. These “junk foods” contain high amounts of chemicals like preservatives, emulsifiers, artificial colorings and dyes. Eating higher amounts of ultraprocessed food may shorten lifespan by more than 10%. These foods have also been linked with inflammation and dysregulation.

Lack of physical activity and higher consumption of ultraprocessed food are both associated with obesity, which is linked to impaired immune function. People should aim for at least 150 minutes a week of moderate to high-intensity exercise and should try to have a diet that emphasizes whole foods such as vegetables, lean meats, beans, whole grains and nuts.

Third, aim for better sleep. Studies have shown that sleep deprivation induces immune changes that increase the risk of various diseases. And people who routinely get fewer than seven hours of sleep a night have a higher likelihood of developing high blood pressure, diabetes and obesity.

There are several methods that can help with improved sleep. Many people struggle because they simply don’t have enough time in bed. Try to prioritize at least eight hours in bed and aim to go to bed and to rise around the same time every day. Other elements of good sleep hygiene include not using screens before sleep and optimizing your sleep environment with a cool, quiet and dark place.

CNN: Are there habits that people should consider stopping to improve their immune systems?

Wen: Yes. The most important are to avoid smoking and excessive alcohol.

Many studies have linked smoking to both short- and long-term effects on immunity, including impairing the body’s ability to fight viral and bacterial infections. Some of these effects are reversed by smoking cessation. Excessive alcohol intake can also weaken immune system response.

Individuals who wish to quit smoking can speak with a physician about options. There are medications that can help in addition to nicotine replacement therapies.

The holidays may be a tough time to cut back on alcohol consumption, but people should try to avoid binge drinking and to keep within guidelines of drinking in moderation (two drinks or less a day for men and one drink or less a day for women on days when alcohol is consumed).

CNN: Is it too late to get vaccinated against respiratory viruses if you are going to family gatherings with newborns or older adults?

Wen: It can take a couple of weeks for the body to build up antibody responses after vaccination. In general, it’s definitely a good idea to be sure you are up to date with your recommended vaccines and to be sure to get your annual flu and Covid-19 vaccines. If you are getting together in, say, a few days from now with vulnerable loved ones, obtaining the shots now probably won’t change your protection during this visit, but it’s still a good idea to get them since it will certainly help you throughout the respiratory virus season.

CNN: What should vulnerable people do to reduce their risk of getting sick during the holidays?

Wen: They should try to avoid crowded settings with many people shouting and speaking loudly. They should consider masking with an N95 or equivalent mask while traveling and in crowded public places.

If they are at especially high risk, they could ask that people visiting them take extra precautions as well. These individuals can also reduce their time spent in crowded settings in the days leading up to a family gathering. And it’s still a good idea to take a rapid Covid-19 test just before seeing especially vulnerable loved ones. The US Food and Drug Administration has newly approved combination flu and Covid-19 tests this season. Free Covid-19 tests are also available from the federal government.

CNN: Are there other virus safety tips people can use to reduce their chance of getting sick during the holidays?

Wen: All of kinds of bugs are going around, including gastrointestinal infections. Don’t forget to wash your hands often and well with soap and water. If you are hosting an event, consider asking those who have signs of respiratory infection like fever and cough to stay home.

And please enjoy the holidays! Loneliness and feeling isolated can actually impair the immune system. The holidays may be tiring and stressful, but being together with those you love — whether it’s family or your family of friends — can bring many benefits to your emotional and physical health.