News Flash

Health - Public Health News

Posted on: August 16, 2021

Natural immunity and vaccine-derived immunity

There are two ways to gain immunity from COVID-19: being infected and surviving (natural immunity) and being vaccinated. While being infected comes with risks such as spreading the disease to family and friends, hospitalization (and its bills), death, and long COVID, vaccination can provide more reliable protection and can boost immunity in people who have previously had COVID-19.

Is natural immunity as good as immunity from vaccination?

Natural immunity is not as effective in preventing COVID-19 reinfection as vaccination, according to a new real-world study released by the CDC.

  • The CDC looked at cases of Kentucky residents who had been infected with COVID-19 in 2020 and identified two groups. 
  • One group had been reinfected in May-June 2021 and the other group had not, but their demographics were otherwise similar. 
  • Scientists compared the vaccination status of the people who had been reinfected with the people who weren’t. 
  • The unvaccinated people were 2.34 times more likely to be reinfected than the fully vaccinated people.

Why is immunity from vaccination better at protecting you than natural immunity? 

study published in the peer-reviewed journal Science indicates that antibodies triggered by vaccination may be better at keeping up with virus mutations than antibodies from natural infection. 

  • Antibodies produced by both natural infection and vaccination target a certain portion of the virus’s spike protein called the receptor binding domain (RBD). 
  • Antibodies from vaccination are able to bind to more sites in this area than antibodies produced by natural infection. 
  • As the virus mutates and changes, including the sites within the RBD, antibodies from vaccination will have more options for binding to the RBD and will have a greater chance of being able to fight infection. On the other hand, antibodies from natural infection may be shut out because they no longer have places in the RBD where they can bind.

How many people have natural immunity?

The CDC uses data from serology (blood serum) tests for COVID antibodies to get a sense of how many COVID infections have happened. This is called a seroprevalence study. The CDC examines data about blood samples from laboratories around the country. 

The CDC estimates that about 6.0% of Washington residents have antibodies from natural infection. This is relatively low as we were able to control infections earlier during the pandemic through masking, social distancing, and other restrictions. Other states have estimates in the 25%-33% range.

However, several states with higher natural immunity percentages are also currently experiencing record-high numbers of COVID-19 hospitalizations and ICU usage, suggesting that this level of natural immunity doesn’t appear to be sufficient for protecting their populations as a whole. These states include:

For more data, visit the CDC seroprevalence study page.

When will we get to community immunity? 

Community immunity, sometimes referred to as herd immunity, is when enough people are immune to a disease that it has a hard time spreading. The number of people changes depending on how contagious the disease is. If it can transmit more easily, then more people need to be immune. 

The Delta variant is more than twice as contagious as the original strain, so the percentage of people who need to be immune in order for us to have gained community immunity also needs to be very high--higher than what was needed to be immune from the original strain. 

Currently, less than 57% of Whatcom residents are fully vaccinated. As noted above, about 6.0% of Washington residents have natural immunity.

The more the virus spreads, the more chances it has to mutate into a more contagious and possibly more deadly version. Waiting for natural infections to get us to community immunity will result in more hospitalizations, deaths, long-term health consequences, and ultimately lead to the evolution of new variants. The toll on our hospital system would be staggering. Please get vaccinated, and please help someone you know get vaccinated, too.

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