The Flu Shot and COVID-19: What You Need to Know

Caesar Djavaherian, MD, MS, FACEP
September 9, 2021
5 mins

Not sure when it’s the right time to get a flu shot? If you’re seeing Halloween decorations or Halloween candy at the drugstore, that’s a good indication it’s time to get one. This flu season, we’re yet again battling not one but two serious and contagious illnesses at the same time. So protect yourself, your family, and your community by getting vaccinated against the flu today. 

Remember that the flu vaccine will not protect you against COVID-19. (Not sure where to get a COVID-19 vaccination in your area? The Carbon Health Vaccine Finder can help you locate a site near you.) And even if you’ve already been vaccinated against COVID-19, you do still need a flu shot.

Keeping Kids as Healthy as Possible

The flu shot is recommended for anyone over the age of six months who does not have any contraindicating factors. Kids who are younger than nine and getting the vaccine for the first time, and kids who have received only one dose of the vaccine prior to July 1, 2020, should get two doses of the vaccine, given four weeks apart. In order to make sure that they are protected during peak season, they should receive the first dose in late September or early October. They won’t be fully protected until two weeks after the second dose. 

Although COVID-19 vaccines are recommended only for children over the age of 12, you can still do your part to ensure that your child stays healthy by vaccinating them against the flu. 

Another way to keep kids safe is to make sure that every eligible person in your household is fully vaccinated against COVID-19. Continue to follow COVID-19 precautions and protocols when in public. Currently, this includes wearing a mask indoors in public indoor settings and continuing to social distance. These measures not only protect your family, but also help keep clinics and emergency rooms from overcrowding. 

Peak Times to Poke 

The flu is detected year-round, but it peaks in the fall and winter. In the United States, flu cases start to rise in October and can remain elevated until May. Historically, the flu peaks most often in February, followed by December, January, and March. The peak month varies from year to year but is defined as the month that has the most confirmed respiratory specimens for influenza infections. You want to make sure you and your family get vaccinated at a time that is most likely to keep you protected during the peak season. 

While drugstores and clinics have made flu vaccines available earlier and earlier each year, it is possible to get the flu vaccine too early, making it less effective. Some evidence suggests that antibodies start to decline four to six months after receiving the flu shot, especially in people older than 65. This means that if you got a flu shot in August, its benefit may decrease by December, potentially leaving you vulnerable during peak season.   

A Side Shot of the Flu Vaccine with Your Breakfast

Older people show a reduced immune response to the vaccine, and researchers have tried to find ways to improve this response. Efforts have included adding adjuvants to vaccines, or agents that enhance the immune response, as well as recommending behavioral interventions, such as aerobic exercise prior to vaccination. Recent research suggests the immune system’s response to a viral antigen or vaccine depends on the time of day. A large randomized controlled trial showed that older people produced a greater antibody response after vaccination when they received the vaccine in the morning hours, as opposed to the afternoon. So it might be better to make the trip to the drugstore or clinic before or after breakfast rather than waiting until after lunch. 

The Flu and Pregnancy: What You Should Know

Pregnant and postpartum people should get the inactivated flu vaccine during early fall, no matter what trimester they are in. This is important because pregnant and postpartum people are at a significantly higher risk of complications from the flu, due to physiological changes in their heart, lung, and immune system function. The live attenuated influenza vaccine is not recommended during pregnancy. The CDC also highly recommends that pregnant and postpartum people get vaccinated against COVID-19, to greatly reduce their chance of contracting the virus. 

Creating an Antibody Army to Protect Your Body

While it’s better to get the flu shot at any time than to not get one at all, remember that there’s a lag time from when you get the shot to when it starts to work. When you get the vaccine, it takes your immune system approximately two weeks to produce protective antibodies, or specialized proteins designed to target specific viral antigens. Antibodies are essentially our bodies’ foot soldiers. During those two weeks, you are not fully protected, so this is another reason to get the vaccine in October and not during those peak months. 

The Flu Shot and COVID-19 Booster Shots

COVID-19 vaccine booster shots can be given at the same time as other vaccines including the flu shot; however, they are currently recommended only for higher-risk populations, including patients with comorbidities and people over the age of 65. It’s possible that the booster shot will be available in the coming weeks or months for all patients 12 years old and older who are six to eight months past their second dose. We will continue to monitor the situation and update the blog as new information becomes available.

Book an appoint today for your flu shot — download the Carbon Health app or visit

Carbon Health’s medical content is reviewed and approved by healthcare professionals before it is published, but it is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Talk to your healthcare provider about questions you may have regarding your health or a medical condition, and before making changes to your healthcare routine.

Caesar Djavaherian, MD, MS, FACEP

As Carbon Health’s Chief Innovation Officer, Caesar Djavaherian, MD, MS, FACEP, guides clinical innovation through product development, service expansion, and partnerships with transformative companies working to improve the healthcare ecosystem. He is an emergency medicine physician, a former high school teacher, and a reformed academic researcher. Caesar co-founded Direct Urgent Care to deliver technology-enabled urgent care throughout the San Francisco Bay Area. He has practiced at New York-Presbyterian Hospital, the University Hospital of Columbia, and Weill Cornell Medicine. In his spare time, Caesar advises healthcare startups, cheers on the Warriors, tries various HIIT workouts, and daydreams about what the future of health will look like.