Effectiveness of vaccines to stop Covid-19
Two types of vaccine against Covid-19 are likely to become more available this spring. The mRNA vaccines from Moderna and Pfizer are approved and slowly being rolled out in the US. They both need to be transported and stored at freezing temperatures which makes distribution more difficult. The Oxford vaccine, which only requires refrigeration, will be easier to transport in rural areas and countries with poorly developed medical infrastructure. All three vaccines require two doses for full protection.
All three vaccines have shown excellent effectiveness in preventing severe cases of Covid-19. Any risk from these new vaccines is clearly much less than the risk of getting Covid-19. I intend to take whichever vaccine is the first to become available to me.
There are some data that show that the Moderna mRNA vaccine and the Oxford vaccine will decrease the amount of community spread but not stop it. People who have been vaccinated may still get mild or asymptomatic cases of Covid-19 so until most people have been vaccinated it will be necessary to wear masks to stop the spread of the virus in the community.
In clinical trials all three vaccines gave good protection from severe Covid and decreased the incidence of disease. Moderna tested volunteers for evidence of infection right before they were given the second dose of vaccine during the clinical trial. More than 2/3 of the people who had gotten asymptomatic Covid-19 infections were the people who had been given a placebo and not the vaccine. Once full immunity is reached after a second dose of vaccine there should be less risk of of any Covid infection, including an asymptomatic one. The amount of immunity for a vaccinated person does decrease over time but it is too soon to know how long that will take.
People who got Covid-19 during clinical trials of the vaccines
Moderna Covid symptoms_____11____________________185
Oxford Covid symptoms_______54____________________165
New clinical trials that involve giving different dosages for the first and second doses of the Oxford vaccine may give better results. Better results may also come from giving a second dose using the Russian vaccine after the initial dose of the Oxford vaccine. Trials will take some time. In the mean time masks can decrease community spread until enough people are vaccinated to get the pandemic under control. This means that people who have gotten the vaccine should wear masks in public and use reasonable caution to avoid infecting others in case they get mild or asymptomatic Covid.
This is a very good popular article:
Here is the Moderna data from the NIH: