Has something been needling you the past year? Has something been jabbing at your brain? Has something pricked the bubble of your hopes and dreams for 2020? Of course! It’s COVID 19! Now, finally, there may be light at the end of the tunnel with the coronavirus vaccine. How does the new vaccine work and what does the data show?
Vaccines work by training the immune system to recognize and kill a foreign invader, such as a virus. Older vaccines work by injecting a dead virus or a weak live viruses to stimulate an immune response. Newer vaccines work by injecting proteins found on the virus and teaching the immune system to mount a defensive response. Vaccines typically take years or even decades before they are ready to be used by the public. The development of a coronavirus vaccine is somewhat of a scientific miracle; the first COVID 19 case was described on December 1 2019, the coronavirus genetic code was sequenced on January 10 2020 and a vaccine was approved by the FDA on December 11 2020. The coronavirus vaccine is not a single vaccine, there are at least six different methods companies are using to attack the virus. Despite the quick turn around on the coronavirus vaccine, the technology behind it has been in development for decades. One method (the vaccine platform used by both Pfizer and Moderna) uses two key components: messenger RNA and the spike protein found on coronaviruses. Messenger RNA takes instructions encoded in the DNA into cells to turn on protein manufacturing. Messenger RNA vaccine technology was invented in the 1990’s and has been constantly refined since then. Work on a spike protein vaccine accelerated after pandemics with severe respiratory syndrome (SARS) in 2003 and Middle East respiratory syndrome (MERS) in 2012, viruses that are similar to coronavirus. The vaccine, containing messenger RNA in a lipid shell, works as follows. The messenger RNA carrying a copy of the spike protein enters a cell. The cell reads the instructions for the spike protein and starts making copies of it. The spike protein moves to the outside of the cell where the immune system detects it. The immune system then learns how to recognize the protein and releases defense mechanisms to kill the infected cells. The second method uses a viral vector (AstraZeneca, Johnson and Johnson and Oxford use this approach). The coronavirus spike protein is introduced into an adenovirus that infects only chimpanzees. The vaccine contains an empty adenovirus with the spike protein inside. This is injected and stimulates the immune system to recognize the spike protein and mount an immune response. Both vaccines teach the body’s own immune system to find and kill the coronavirus.
The data on Pfizer’s messenger RNA vaccine was just reported. The trial enrolled 43,448 people, all 16 years of age or older. The vaccine was administered in two doses, 21 days apart and patients were followed for two months. The efficacy of the vaccine in preventing symptomatic COVID 19 was excellent at 95%. The efficacy was good for all groups: 94% for those over 55 years old, 96% for men, 94 % for women, 95% for whites, 100% for blacks, 94% for Hispanics and 94% for those with hypertension. For comparison, the efficacy of the measles vaccine is 97%, the chicken pox vaccine is 82% and the flu vaccine varies from 50% to 60%. Side effects were generally mild and included pain at the injection site, fever, fatigue, headache and muscle or joint pain. In general, reactions were milder and less common in older patients (> 55) compared to younger patients. Reactions were more common after the second dose compared to the first dose. Side effects are similar to the reactions seen after the shingles vaccine. It is not known whether the vaccine can prevent COVID 19 in children under 16 years old, pregnant women and immunocompromised patients. In addition, the study could not determine whether the vaccine prevents asymptomatic infection. Lastly, patients in the placebo arm will have to be offered the vaccine since the FDA approved it. It is unethical to withhold vaccine for these people. This means that long-term efficacy and safety will be determined by real world experience. Based on this data, the FDA gave the Pfizer vaccine emergency use authorization on December 11 2020. The first dose of this vaccine was given to a 90-year-old woman in England on December 8 2020. Moderna is conducting a 30,000 person trial with a similar vaccine. The preliminary results show good efficacy (also 95%) and safety but the final results are still pending.
The Oxford adenovirus vector vaccine was studied in 23,849 people over the age of 18. This was also a two-dose regimen. The efficacy was 62% in patients who received two standard doses and 90% in those who received a low dose followed by a standard dose. The side effect profile was also very low. Johnson and Johnson’s vaccine works in a similar fashion. A 60,000 person trial was put on hold due to a serious adverse reaction but has recently resumed. Results from the trial are pending.
To contain coronavirus, it is estimated that 60% of the population will need to be vaccinated to achieve herd immunity. This may be difficult for several reasons. First, enough vaccine must be manufactured and distributed. There are many logistical obstacles. Next, enough people must consent to take the vaccine. A recent poll of Americans found that 29% would definitely take the vaccine and 31% would probably take it. That adds up to 60% with no room for error. In addition, a poll among health care workers in New Jersey revealed only 50% were planning on taking the vaccine. This is disappointing since the CDC guidelines will have health care personnel vaccinated first along with long term nursing home residents in Phase 1a. Phase 1b will be essential workers (police, fire, corrections officers, transportation workers, food and agriculture workers and teachers). Phase 1C will include adults with high-risk medical conditions and adults over age 65.
Some caveats:
The efficacy of the vaccine is excellent (better than the annual flu vaccine with an efficacy of only 50-60%).
It seems that the vaccine-induced immune response is stronger than that of the natural COVID 19 infection.
The side effect profile is similar to other vaccines (such as the shingles vaccine).
The coronavirus is not being injected. You cannot get COVID 19 from the vaccine.
The vaccine will not alter your DNA.
So once it is available, please line up to get your vaccine. It will help your herd tremendously.
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