After the first dose of the vaccine, the total effectiveness of all COVID-19 vaccines in our study was 71% (95% CI 0.65, 0.78). The total effectiveness of vaccines after the second dose was 91% (95% CI 0.88, 0.94)).

Vaccine effectiveness against COVID-19 infection For the Pfizer and ASZ vaccines, the results showed that their protection against infection declined from 93.2% and 90.2%, respectively, during the first three months to 91.4% and 89.3% during a six-month interval.

At 2–3 months and ≥8 months after receipt of the most recent monovalent dose, rVE of a bivalent mRNA COVID-19 vaccine dose was 30% and 56% among persons aged 18–49 years, 31% and 48% among persons aged 50–64 years, and 28% and 43% among persons aged ≥65 years, respectively.

Once you have had COVID-19, your immune system responds in several ways. This immune response can protect you against reinfection for several months, but this protection decreases over time. People with weakened immune systems who get an infection may have a limited immune response or none at all.

The immune systems of more than 95% of people who recovered from COVID-19 had durable memories of the virus up to eight months after infection.

“High levels of antibodies likely last for four to six months after infection with Omicron, as for earlier variants, in most otherwise healthy individuals,” Moss said.

Can you get Covid-19 twice? Yes, it is possible to get Covid-19 two, three or even more times.

Reinfection with the virus that causes COVID-19 occurs when you are infected, recover, and then get infected again. You can be reinfected multiple times. Reinfections are most often mild, but severe illness can occur.

FRIDAY, Feb. 17, 2023 (HealthDay News) -- Natural immunity acquired from a COVID infection provides strong and lasting protection against severe illness if a person becomes reinfected, a new evidence review has concluded.

Other studies, including a meta-analysis of the effectiveness of COVID-19 vaccines and natural immunity, showed similar results to the PiratePACT study, with natural immunity waning after about 140 days in that cluster of studies.

Vaccination Offers Greater Benefits Than Natural Immunity In February 2023, a report came out that found that natural immunity provided protection from the virus at least as good as immunization, spurring debate about which was better.

Many health care workers and others have never contracted the disease despite being heavily exposed. Scientists around the world are studying whether genetic mutations make some people immune to the infection or resistant to the illness.