As more Covid vaccines are being distributed, your patients will have questions, including which one is better. At the time of this writing, the FDA granted emergency-use authorization (EUA) to two vaccines: Pfizer-BioNTech and Moderna. Two other vaccine candidates from Johnson & Johnson and AstraZeneca are also waiting in the wings to apply for an EUA.

With all the news coverage highlighting clinical trial results, sometimes vetted, sometimes not, Americans are starting to question which vaccine they should get. The truth is the best vaccine is the one that is in your body.

Here we lay out information about each vaccine that could help you answer your patient’s questions about the available vaccines and even the ones waiting in the wings. Ultimately, patients will not be able to choose which vaccine they receive; they will receive the one offered where they are being vaccinated.

What Are the Different Vaccine Types? Does It Matter Which Covid-19 Vaccine I Get?

The Pfizer and Moderna vaccines rely on relatively new vaccine technology called mRNA. It is a technology that uses a bit of genetic code via single-strand RNA and delivers it to cells making a spike, or surface protein, on the virus, activating the immune system.

The Johnson & Johnson and the Oxford-AstraZeneca vaccines are viral vector vaccines that use adenovirus engineered to carry a double-stranded DNA of the SARS-2 spike protein and introduce it to our body’s immune system. This vaccine technology was also used to make the Ebola vaccine authorized by the European Medicines Agency.

While there are differences in efficacy rates, the most significant difference between the vaccines is how they are stored. The mRNA vaccines are less stable, so they must be kept in extremely cold temperatures. In comparison, the viral-vectored vaccines are sturdier because they use virus DNA (i.e., two strands compared to one) and don’t need the ultra-cold freezers.

Are Certain Vaccines Better for Different Age Groups?

The short answer is no. For the time being, none of the vaccines have been tested in children, though Moderna is running a trial with 12- to 17-year-olds. Data might be available in May. Otherwise, the Pfizer vaccine is approved for patients over 16, and the Moderna vaccine is approved for patients over 18. Also, Johnson & Johnson and the Oxford vaccines only have data on patients who are 18 or older.

The Pfizer and Moderna Vaccines Have Efficiencies in the 90s. Shouldn’t I Get Vaccinated With One of Those?

Comparing the efficacies of each Covid vaccine against the other isn’t an apples-to-apples assessment because the clinical trials didn’t measure effectiveness the same. For instance, Pfizer and Moderna looked at preventing symptomatic Covid-19; Johnson & Johnson sought to determine if it protected against moderate-to-severe Covid-19; and Oxford-AstraZeneca had reported efficiency for one-shot and two-shots.

All the vaccines will help minimize symptoms if someone is infected with SARS-CoV-2. Only the Johnson & Johnson and the Oxford vaccines have data on the emerging strains. However, the thought is that the high levels of efficiency seen in the Moderna and Pfizer vaccines might be less so against the strains but still offer some protection.

Should I Be Worried About Side Effects From the Covid Vaccine?

Like many vaccines, there might be pain and swelling at the injection site. In addition, side effects could also include fever, chills, tiredness, and headaches. But, as you know, these are signs that the immune system has been activated. These side effects might be more intense after the second shot or if the patient has had Covid-19 previously. In addition, if your patient is worried about past allergic reactions to vaccines, the CDC suggests observing them for 30 minutes rather than 15 minutes afterward.

Can I Get Vaccinated if I Have HIV or Have a Compromised Immune System?

While no data establishes the safety and efficiency of the Moderna and Pfizer vaccines, these individuals are at higher risk of experiencing severe Covid-19. Therefore, they should receive the vaccine unless otherwise contraindicated. In addition, the CDC suggests counseling them about the potential for reduced immune responses and the need to follow all current guidelines.

After I Have Been Vaccinated, Can I Resume Life As Normal?

Encourage your patients to think about moving forward, not returning to normal. The vaccination is one way to do so, but depending on when they get their vaccine, continued mask-wearing is suggested since many may not be vaccinated. Also, avoid large groups of people. Information about how the vaccines hinder transmission isn’t entirely understood, so masking helps reduce those possibilities until herd immunity is reached.

How Long Will I Be Protected?

The honest answer is that no one knows for sure. Reporting in STAT suggests that a large part of figuring this out will involve watching for cases of Covid occurring in those vaccinated. If this happens in large numbers, we will probably start seeing recommendations for booster shots.