How Long After Getting the COVID-19 Booster Are You Immune?

The SARS-CoV-2 virus is a contagious pathogen that causes the respiratory infection known as COVID-19. Since it emerged in late 2019, the virus induced a global pandemic and wide-scale lockdowns before a vaccine was developed.

Now, there are many variations of the original virus, and the vaccines first developed in late 2020 have been updated to match new and prominent variants of the coronavirus.

This article will explore the current vaccination guidelines and describe what a booster is and if you'll need one.

How COVID-19 Boosters Work

When you are vaccinated against a particular virus, your immune system gets information from the virus, allowing your body to mount a defense and fight off the infection. The immunity you develop is similar to your natural immunity against a virus after overcoming an active infection—without having to get sick first.

Like many living things, though, viruses evolve over time. More than 20 recognized variants of the COVID-19 virus have emerged in the years since the first COVID-19 vaccines were formulated.

Boosters are updates to the original vaccine you received. These updates contain additional information about new or mutated viruses to offer you protection against the latest variants.

The Centers for Disease Control and Prevention (CDC) recommends that all American adults receive at least one of the latest vaccine updates. These updates protect against newer variants of COVID-19 and boost the work of the original vaccine, as its effectiveness can fade over time.

There are several brands of COVID-19 vaccines, and the CDC does not recommend one over another.

How Soon the Booster Works

How long it takes a vaccine or booster to offer protection and how long protection lasts can vary from person to person. Infants, older adults, and people with weakened immune systems may not develop strong responses to the vaccine and may require additional doses or boosters.

Data from vaccine manufacturers suggest that, for most people, vaccines and booster doses start protecting you against the coronavirus within a week or two after your injection. However, specific factors, discussed later, can play a role in how quickly you develop immunity against COVID-19.

Does the Vaccine Type Matter?

The CDC does not recommend one of the currently available vaccines over another as long as it's age-appropriate. Revised vaccines and boosters are formulated to protect against the latest variations of the virus. There are some slight differences in the types, how they work, and what recommendations have been made for boosters.

The two types of COVID-19 vaccines are:

• Messenger RNA (mRNA): The Pfizer-BioNTech and Moderna vaccines are developed using lab-created proteins that mimic the virus that causes COVID-19. These proteins give your immune system genetic information about the virus (without using any of the virus itself) to help your body mount its own protection.
• Protein subunit: The Novavax vaccine uses subunits (tiny pieces) of the virus to deliver protection. Vaccines like Novavax use spike proteins similar to what appears on the actual virus. This helps your body to develop a response and protection against these proteins when it encounters the actual virus.

Both types of vaccine offer similar levels of protection, but the Novavax vaccine is not provided to children under 12. According to the CDC, each vaccine is updated to protect against the newest or most commonly circulating strains of COVID-19.

Talk to a healthcare provider to determine which COVID-19 vaccine or booster is right for you.

How Long Does Immunity Last?

How long protection lasts can also vary from person to person, but research suggests that strong protection against COVID-19 infection lasts for about five months after vaccination. Beyond that, immunity can weaken, but you will still have some protection.

A study published in spring 2023 revealed that even vaccines that had lost the ability to prevent infection completely were helpful in preventing hospitalization or death from a severe COVID-19 infection.

How long your protection lasts will depend on the strength of your immune system, how many total vaccinations and boosters you have received, and what new variants or strains emerge that might not be covered by your last booster formula.

Factors That Affect Immunity After COVID-19 Boosters

Your overall health can impact how effectively and quickly your body develops protection after immunization and how long protection lasts.

Comorbidities (co-occurring illnesses or conditions) and chronic health problems can impact the strength and response of your immune system, so things like cardiovascular disease, autoimmune disease, and gastrointestinal diseases can limit the strength and duration of the protection your vaccine or booster provides.

Other factors that can influence the strength and duration of your protection after a COVID-19 vaccine or booster include:

• Age
• Alcohol use
• Diet
• Exercise habits
• Genetics
• Having obesity
• Medications you are taking
• Prior infection history
• Sex
  
• Sleep patterns
• Smoking
  
• Stress
  

Some vaccine-specific factors can affect how well an immunization works. This includes the dose you receive, the timing of your immunization, and what other vaccines or medications you may have received simultaneously.

Summary

Several vaccines and boosters have been developed since the COVID-19 virus emerged in late 2019. If you have not been vaccinated or received an updated vaccine after September 2023, the CDC recommends you receive an updated COVID-19 vaccine to ensure the most adequate protection from newer strains of COVID-19.

Talk to a healthcare provider if you are sick, have complex medical problems, or have other concerns about how well you will respond to the vaccine or a COVID-19 booster.