How are the Moderna and Pfizer Vaccines Different?

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In one of the swiftest vaccine developments in history, global teams of drugmakers, researchers, and scientists laid the groundwork that spurred the production of vaccines to end the coronavirus pandemic. Hundreds of vaccine candidates were developed globally in clinical trials in the fight against the deadly virus. As of the time of writing, only a few have completed trials and have demonstrated efficacy and safety of the vaccines in record time, the two most popular of which are the Moderna and Pfizer vaccines.

The COVID-19 vaccines by drugmakers Moderna and Pfizer entered the market as soon as their promising trial results were made public. The US Food and Drug Administration (FDA) officially authorized Moderna’s COVID-19 vaccine for emergency use on December 18 after an FDA panel recommended the vaccine for use. The approval for Pfizer’s COVID-19 vaccine came a week earlier and had already been distributed to frontline health workers and residents of long-term care facilities.

Although both vaccines are already being rolled out to priority groups in the US, they differ in more ways than one. Here are a few differences you should note:

Vaccine Efficacy

While both vaccines have shown outstanding degrees of efficacy, they are not equally effective. Further, they both differ in their effectiveness across age groups.

The Pfizer vaccine showed 95% efficacy in preventing symptomatic COVID-19 infection, starting from seven days after the second dose. On the other hand, the Moderna vaccine was found to be 94.1% effective in preventing asymptomatic COVID-19 infection, starting from 14 days after the second dose.

Unlike the Pfizer vaccine that showed equal effectiveness across all age groups, the Moderna vaccine appeared less effective for people 65 and older. However, each vaccine demonstrated equal effectiveness across all age groups.

Barring these nuances, both vaccines are highly effective at preventing COVID-19 after the second dose.

Age Limit

Both vaccines have slightly different target populations. The Pfizer coronavirus vaccine was approved for use in people aged 16 and older, while only people aged 18 and older can receive the Moderna vaccine.

The age difference in the target populations is reflective of the age groups that were enrolled in the respective study trials. However, Moderna has commenced testing its vaccine in 12 to 17-year-olds.

Dosage and Dose Interval

One similarity between both Moderna and Pfizer vaccines is that both require two shots; an initial priming dose, then a booster shot administered much later; however, the difference lies in the interval between both doses.

Moderna’s booster dose is administered after 28 days of the priming dose, while Pfizer’s is administered 21 days after the priming dose. Another difference is the dosage in each shot. Each dose of the Pfizer vaccine contains 30 micrograms of the vaccine, while Moderna uses 100 micrograms of vaccine for each dose.

Storage Requirements

Both vaccines vary widely in this regard. The Pfizer vaccine must be stored and transported in specially-designed, temperature-controlled thermal shippers that can maintain temperatures around -70 degrees Celsius (-94 degrees Fahrenheit). The vaccine can be stored in these conditions for up to 10 days, after which it should be stored in ultra-low temperature freezers for up to six months. According to Pfizer, the vaccine can also be stored in hospital-type refrigeration units at 36-46 degrees Fahrenheit for up to five days.

On the other hand, the Moderna vaccine has to be shipped at 20 degrees Celsius (-4 degrees Fahrenheit) and can be stored in refrigeration units between 36 to 46 degrees Fahrenheit for up to 30 days. The vaccine will remain viable at -20 degrees Celsius for up to six months and room temperature for only 12 hours.

These differences show that the Pfizer vaccine is less stable. The drugmakers say the difference in storage requirements is because of the different lipid components in both vaccines.

Minimum Purchase Order

The minimum amount of vaccine doses you can order for either vaccine are not the same. For the Pfizer vaccine, you need to order at least 975 doses for your purchase to be valid. This may be challenging for individuals or small employers who need only a few doses.

The Moderna vaccine does not require as many doses to make an order. A minimum of 100 doses and your order is confirmed. Further, while the Pfizer vaccine is shipped in five-dose vials, Moderna’s vaccine is shipped in 10-dose vials.

Safety Profiles

According to a fact sheet provided by the FDA regarding Pfizer and Moderna coronavirus vaccines, both vaccines may cause only minimal side effects, such as injection site pain and swelling, tiredness, headache, muscle pain, fever, joint pain, nausea, and vomiting.

During trials, some participants who received the Pfizer vaccine reported severe allergic reactions. This has led the pharm giant to warn of a “remote chance” that the vaccine could cause a severe allergic reaction within minutes to an hour of getting a dose. Although there were no risk of serious allergic reactions to the Moderna vaccine, the FDA still advises caution for those who have a history of severe allergic reactions,

Both Vaccines are Still Very Similar

Barring these variations, the Pfizer and Moderna vaccines still have many similarities, one of which is how they work. Both vaccines are messenger RNA (mRNA) vaccines, which work by encoding a portion of the spike protein with which the coronavirus attaches to the body cells. The mRNA instructs the body cells to produce the encoded pieces of the spike protein and presents them to the body’s immune cells to generate antibodies that will recognize and attack any particle that contains the proteins.

Once the body produces these antibodies, both the protein and the mRNA are eliminated, and the antibodies continue to guard your body against a similar spike protein in the future.

Both vaccines are different from conventional vaccines, which are made from viruses grown in animal cells or chicken eggs, and are inactivated or killed before they are administered.

For now, it’s uncertain how long both vaccines protect. This would involve monitoring those who have already been inoculated and performing serial antibody tests to determine how the antibodies reduce over time. This would also involve watching for reports that people who had received the vaccine are contracting COVID-19 in large numbers.