One-Dose Verses Two Vaccines for Covid
Currently, three Covid vaccines are being used in the United States. The Covid vaccines made by Pfizer and Moderna require two doses. The Johnson and Johnson Covid vaccine requires one dose. Why is there a difference in doses needed, and what does it mean for you?
According to the College of Physicians of Philadelphia, all vaccines are subject to many research and development stages and testing. One of the final tests for a vaccine is a Phase III Clinical Trial. During this testing, many people volunteer to either be given the potential vaccine or be given a placebo, a harmless injection.
The volunteers do not know which group they are in, and the researchers are not told when the injections are given. This double-blind type of study allows researchers to analyze the data and outcomes without bias. It protects researchers from making assumptions or assigning possible outcomes only to the vaccinated group.
In the clinical trials, the Johnson and Johnson Covid vaccine had 85% efficacy against developing Covid disease. The other Covid vaccines had 95% efficacy after two doses. The first dose of these vaccines did not provide enough protection to warrant authorizing their use. Since part of the clinical trial was to determine the effective dose, the participants received a second dose, which proved to increase the immunity.
It is not uncommon for vaccines to require two doses for maximum immunity. The first dose helps your body’s immune system recognize a virus, while the second dose boosts your immune response.
Some other vaccines that require two doses include:
- Hepatitis B
Is 85% efficacy enough?
According to the CDC, no vaccine is 100% effective. There may always be people who cannot receive a vaccine because of health or age issues, and not everyone responds to vaccines strongly to build enough antibodies for immunity.
However, people who are not immune can only get Covid if they are exposed to the virus. People who are infected spread the virus, so if enough people are immune, the risk that someone will come into contact with the virus drops dramatically. This is known as herd immunity.
When a majority of the population is immune, it protects others who cannot receive a vaccine. Scientists estimate the between 60%-70% of the population needs immunity to Covid for herd immunity to work. People who are not vaccinated and haven’t had Covid have no immunity. The more people that are vaccinated, the greater the chance the population will reach herd immunity.
All three Covid vaccines are being used under Emergency Use Authorization from the Food and Drug Administration (FDA). The FDA analyzed the clinical trials’ results and determined the vaccines were safe and effective enough to use in the general population. An Emergency Use Authorization is only granted when there is an urgent need for a safe and effective vaccine. According to the World Health Organization (WHO), the threshold for efficacy for Emergency Use Authorization is 50%. All three Covid vaccines are well above this threshold.
Guidelines for Vaccinated People
Regardless of which Covid vaccine you get, the CDC states it takes 14 days after the last dose to develop full immunity. Because your immunity is much greater than someone who isn’t vaccinated, the CDC relaxed some social distancing guidelines for fully vaccinated people.
These guidelines state that fully vaccinated people can:
- Visit inside a home or private setting without a mask with other fully vaccinated people of any age.
- Visit inside a home or private setting without a mask with one household of unvaccinated people who are not at risk for severe illness.
- Travel domestically without a pre-or post-travel test.
- Travel internationally without a pre-travel test depending on destination.
- Travel domestically and internationally without quarantining after travel.
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