Even before they were approved for emergency use, many media outlets and public health experts were enthusiastic about vaccines designed to prevent or mitigate COVID-19 infections. Most people hope that an effective COVID-19 vaccine will help us participate again in school, business and social gatherings. The experience so far has been impressive, as millions of people bared their arms for shots. We still need to finish the job, getting children vaccinated as well as adults. However, experience both in the US and the UK is very encouraging.
How Well Does Pfizer or Moderna COVID-19 Vaccine Work?
Preventing COVID infections remains a high priority. Both the Pfizer/BioNTech and the Moderna COVID-19 vaccines are proving very effective in this effort. A study in the CDC publication, Morbidity and Mortality Weekly Report, reveals that people over 65 who have had both shots reduce their risk of hospitalization by 94% (MMWR, April 28, 2021). The researchers evaluated patients at 24 hospitals in 14 states. Partially vaccinated people reduced their risk of hospitalization by about 64%. That is certainly good, but not as impressive as the protection from full vaccination. It makes sense to get both shots.
These real-world findings are similar to those from the clinical trials of the vaccines. Read on to learn more about the experience in England and Israel with vaccines. We also cover questions that people were asking even before the vaccines became available.
How Long to Wait Between Shots:
Researchers in the UK report that the Oxford-AstraZeneca vaccine that reduces serious illness and deaths from COVID-19 also helps cut viral transmission (Preprints with The Lancet, Feb. 1, 2021). Investigators swabbed trial volunteers every week after they got their first shot. The preliminary analysis suggests that the vaccine could be slowing the spread of the virus.
Ongoing clinical trials also show that a span of three months rather than three weeks between the initial shot and the booster increases the effectiveness of this COVID-19 vaccine. Efficacy of 55% when the two shots are less than six weeks apart rises dramatically to 82% when the shots are three months apart. The single shot alone is 76% effective, based on data from 22 to 90 days after the initial vaccination.
COVID-19 Vaccine Development Proceeded at “Warp Speed:”
Scientists usually take years to develop a vaccine against a brand-new disease. An unusual public-private partnership dubbed Operation Warp Speed reduced development time dramatically. Many government agencies, such as the Department of Health and Human Services (HHS), including the Centers for Disease Control and Prevention (CDC), the Food and Drug Administration (FDA), the National Institutes of Health (NIH), and the Biomedical Advanced Research and Development Authority (BARDA), along with the Department of Defense (DoD) provided support and funding to pharmaceutical firms. This allowed the firms to put all their resources into development without worrying about whether or not they would be able to market the products. In addition, they were able to utilize existing research on mRNA technology without building it from scratch.
Consequently, the development and production of COVID-19 vaccine was unprecedented. Before the end of 2020, the FDA had given Emergency Use Authorization to two vaccines, one from Pfizer/BioNTech and one from Moderna. Now, states are scrambling to use their allotted shots to immunize their citizens.
Good News on Vaccination from Israel:
Israel has vaccinated a higher proportion of its citizens than most other countries. A preliminary study compared 200,000 vaccinated people over 60 with a matched group of 200,000 waiting for their shots. Within two weeks of receiving the first vaccination, people were a third less likely to become infected with COVID-19.
Another study suggested that the first dose offered almost 60% protection within two to three weeks. After receiving both doses of the Pfizer/BioNTech vaccine, fewer than 1% of Israelis came down with COVID. These data are preliminary but promising. They suggest that the vaccine might be even better than 95% effective.
Where Do We Stand With a COVID-19 Vaccine?
mRNA Vaccine:
Messenger RNA (mRNA) vaccines have not been used before, but they triggered a robust immune response in early trials. Both Moderna and Pfizer developed mRNA vaccine candidates under the auspices of Operation Warp Speed (JAMA, July 6, 2020). After phase 3 testing, both vaccines are considered 95% effective in preventing serious illness. They are now part of the vaccination campaign in the USA.
Viral Vector Vaccine:
Some vaccines use a living virus that has been “attenuated” so that it no longer causes illness to carry the antigen into the body and alert the immune cells to defend against it. Such viruses can replicate, but they don’t make people sick. Hopefully, though, they will trigger an effective immune response against SARS-CoV-2. Operation Warp Speed funded such a COVID-19 vaccine from Merck Sharp & Dohme. Unfortunately, however, the company concluded it was not effective enough. On January 25, 2021, it announced that it was discontinuing vaccine development and focusing on drugs for treatment.
Spike Protein Vaccines:
Two other vaccine candidates use carrier viruses that can’t replicate themselves. AstraZeneca and Johnson & Johnson are using Operation Warp Speed funding to develop such vaccines that present the coronavirus spike protein to immune cells in the body. Like the mRNA vaccine, this relatively new technology has not been widely employed before now. Unlike the mRNA immunizations currently being administered, these vaccines require only one shot.
The Johnson & Johnson vaccine won Emergency Use Authorization in the US in February, 2021. The Oxford-AstraZeneca vaccine is being widely used in the UK and has been approved for use in the EU. Both of these vaccines can, in rare instances, cause dangerous blood clots, but the FDA and most European health regulators have determined that the benefits outweigh the risks.
What Is the Expected Outcome?
Even with effective vaccines available, however, public health personnel are struggling to distribute them widely. They are racing against time to vaccinate people before the SARS-CoV-2 virus mutates too much. The immune system needs weeks to react effectively to a vaccination. The mRNA vaccines require two doses three or four weeks apart, necessitating a second appointment.
In addition, vaccines are rarely 100% effective. Even a vaccine that offers 95% protection is not perfect. It won’t quite take the world back to a pre-pandemic situation. However, vaccinated adults can safely enjoy the outdoors unmasked, unless they are in a dense crowd. Still, people need to maintain vigilance. The new virus variants make this more urgent than ever.
