Natural Immunity vs. Vaccine-Acquired Immunity: Which Is Better?
Is it better to acquire immunity via infection or vaccination?
The human immune system develops the same antibodies in response to, say, chickenpox infection and chickenpox vaccination. People who have had chickenpox and people who received the chickenpox vaccine are well-protected from future infection. In both cases, the body “remembers” and can quickly generate an immune response to attack the chickenpox virus if it’s encountered again.
Some people think that natural immunity—developed after infection—is preferable to vaccine-acquired immunity. Both types of immunity (natural and acquired) have pros and cons. Learn more about natural vs. acquired immunity, including what’s known about natural immunity vs. vaccine immunity for COVID-19.
For some infectious diseases for which there are vaccines, natural infection brings about stronger immunity than the vaccine-acquired immunity. According to the Children’s Hospital of Philadelphia (CHOP), “immunity from disease often follows a single natural infection [but] immunity from vaccines usually occurs only after several doses.” That’s the case with chickenpox—you're usually immune after just one bout of chickenpox, but humans need two doses of chickenpox vaccine to develop effective and long-lasting immunity.
One reason natural immunity is so powerful is because people don’t usually develop illness in response to germ encounters unless they are exposed to a large amount of virus or bacteria. The immune system mounts a strong response to this high “dose” of germs. This powerful response is also responsible for many of the uncomfortable symptoms you feel when you’re sick, such as fatigue, fever, and chills.
On the other hand, countless germs, such as human papillomavirus (HPV), evolve to escape detection by the immune system. A healthy immune system eventually clears HPV in 90% of cases, but people who are immunosuppressed are especially vulnerable to long-term infection as well as reinfection.
The biggest downside of natural infection is there’s no way to know, in advance, how serious the infection will be. In most people, chickenpox is an uncomfortable annoyance. But some people also develop a lung infection, swelling of the brain, or life-threatening blood infection. Before chickenpox vaccinations were widely available, approximately 10,000 people in the United States were hospitalized with chickenpox complications each year, and about 100 people died of chickenpox annually.
Vaccines stimulate the body to produce the antibodies and memory cells necessary to fight specific infections. The chickenpox vaccine contains tiny amounts of weakened (attenuated) chickenpox virus—enough to cause the immune system to start cranking out antibodies, but not enough for the body to develop chickenpox blisters. The polio and influenza vaccines contain dead (inactivated, or “killed”) viruses; they can’t cause disease, but they kick the immune system into action. COVID-19 mRNA vaccines teach cells how to make spike proteins like those on the coronavirus, and the body then develops antibodies against those proteins.
Although side effects, such as soreness and fever are common after vaccination, most people don’t feel nearly as lousy after vaccination as they do when they contract an infection.
In some cases, vaccine-acquired immunity is stronger than natural immunity. According to CHOP, HPV, tetanus, Haemophilus influenzae type b (Hib), and pneumococcal vaccines induce a better immune response than natural infection.
Researchers are still learning about natural and vaccine-induced immunity for COVID-19. At present, healthcare providers believe that both COVID-19 infection and COVID-19 vaccination produce immunity that likely lasts at least eight months. This immunity is not complete; it’s possible to contract COVID-19 after COVID-19 vaccination or an earlier bout of infection, though these cases are not usually severe.
Some evidence suggests that COVID-19 vaccination after infection can “sharpen immunity.” Vaccination after COVID-19 recovery increases antibody production and reduces the frequency of reinfection, according to several studies.
Acquired immunity is safer than natural immunity. For all vaccine-preventable illnesses, the risk of developing a serious vaccine-related side effect is much smaller than the risk of serious complications if infected. A person who contracts COVID-19 is at risk of hospitalization and long-term side effects, including post-COVID-19 syndrome (or “long-haul COVID”). There are known risk factors for severe COVID-19, such as heart disease, but thousands of people with none of those risk factors have developed severe COVID-19. A person who receives the COVID-19 vaccine is unlikely to require hospitalization or develop post-COVID-19 syndrome.
In most cases, healthcare experts recommend vaccination over natural infection, when available. If you have questions about natural and acquired immunity, talk to your healthcare provider.