How immunity works and why it needs a boost

COVID-19 infections are skyrocketing across Oregon. We’re seeing a sharp increase in breakthrough cases among the vaccinated, and previously infected unvaccinated people are being infected for a second time. This increase is in part because immunity wanes and in part because mutations in Omicron allow it to evade previously acquired immunity. 

There are only two ways to restrengthen our immunity: 1) to be infected by the COVID-19 virus or 2) to get a booster dose. Infection could lead to hospitalization, damage to the lungs and even death. Even mild cases can result in COVID-19 “long-haulers” who have symptoms for months. 

Here are some key terms to understanding immunity

Antibodies are proteins produced by the body to neutralize or destroy toxins or disease-carrying organisms when they enter your body. Antibody levels typically peak in the month after vaccination or infection, and then begin to decline, still offering strong protection for several months. The mutations in the Omicron variant may allow it to avoid some of these antibodies, but antibodies do still offer a defense. The antibodies made from COVID-19 infections or vaccinations are specific to coronaviruses and do not fight other diseases, like the flu. 

Memory B-cells are built during the month after vaccination or infection. These cells stand guard, ready to produce antibodies quickly and take action if they spot the same invading organism. They remain in the body for years, and although they may not prevent infection, they can reduce the severity of illness. 

T-cells are white blood cells that attack other cells that have been infected by the virus.  

Natural immunity comes from being infected by the COVID-19 virus, so it comes with a cost: to get this immunity you have to survive the illness, which may be severe, during which time you can spread the virus to others. The degree of natural immunity after infection varies from person to person. Research suggests that somebody with a severe case of COVID-19 likely builds a stronger immune response than somebody who has a mild case or no symptoms at all. Like vaccine immunity, natural immunity to COVID-19 wanes over time. 

Vaccine immunity comes from being vaccinated. The vaccine introduces your immune system to a protein from the virus, allowing you to build up antibodies or memory B- and T-cells to fight COVID-19 without being infected. Vaccination can boost any natural immunity a person may have from being previously infected. 

When somebody with sufficient antibodies is exposed to COVID-19, they immediately fend off the virus, which prevents infection. As antibody levels drop, the virus may be able to infect the person; but memory B- and T-cells remain in place and give the immune system a decent chance to fight COVID-19 and prevent severe infection. This is why we see breakthrough cases or reinfection as immunity wanes, and also why vaccinated people usually avoid severe illness and death when they test positive for COVID-19.

Boost your immune system with a booster.

But better than a primary series (usually two shots) is to get boosted. Booster shots rebuild antibodies quickly, within a few days, even quicker than the original vaccination—because those memory B cells respond quickly. This rapid rebuild also happens when an unvaccinated person previously infected with the COVID-19 virus gets their first vaccination.   

Which brings us back to Omicron. Studies show that the variant is evading our vaccinated immune systems to a degree that, over time, leaves vaccinated people only 35% protected against a COVID-19 infection. But with a booster shot of Pfizer or Moderna, that protection jumps to 75%. 

When you’re not infected with the COVID-19 virus, you won’t get sick from it, you won’t end up in the hospital and you won’t spread it to others. Vaccinations and boosters remain the best way to keep you and your community safe and healthy.  

Visit the CDC website for a more in-depth explanation on how natural and vaccine immunity work.