There are several vaccines that are in use. The first mass vaccination program launched in early December 2020 and as of and as of 15 February 2021, 175.3 million vaccine doses have been administered. At least 7 different vaccines have been administered.

WHO issued an Emergency Use Listing (EULs) for the Pfizer COVID-19 vaccine on 31 December 2020. On 15 February 2021, WHO issued EULs for two versions of the AstraZeneca/Oxford COVID-19 vaccine, manufactured by the Serum Institute of India and SKBio.

Because COVID-19 vaccines have only been utilized in the past several months, it’s too early to realize the length of protection of COVID-19 vaccines. Study is in progress to answer this question. However, it is promising that existing data suggest that most people who recover from COVID-19 get an immune response that provides at least some period of protection against reinfection – although we’re still learning how strong this protection is, and how long it lasts.

In the contest to end the coronavirus pandemic, the more secure, efficient vaccines we have available, the sooner we will be able to move up out of this mess.

To date, five vaccines — produced by Moderna, Pfizer, Novavax, Johnson & Johnson and AstraZeneca — are the front-runners. In the coming months, these vaccines will not only save tons of lives, but they will also relieve some of the tremendous pressure on the health care system and provide our frontline workers with some much-needed rest.

Some of these vaccines (like Johnson & Johnson’s) were tested in areas where more contagious variants have taken hold, such as South Africa, whereas Moderna’s and Pfizer’s vaccines were tested before the variants identified in the U.K. and South Africa struck and began spreading like wildfire.

The Pfizer and Moderna vaccines have shown astonishing — and essentially equivalent — degrees of efficacy, at least in the early stages after vaccination.

The Pfizer vaccine showed efficacy of 95% at preventing symptomatic Covid infection after two doses. The vaccine appeared to be more or less equally protective across age groups and racial and ethnic groups.

The Moderna vaccine was 94.1% effective at preventing symptomatic Covid-19, after the second dose. The vaccine’s efficacy appeared to be slightly lower in people 65 and older, but during a presentation to the Food and Drug Administration’s advisory committee in December, the company explained that the numbers could have been influenced by the fact there were few cases in that age group in the trial. The vaccine appeared to be equally effective across different ethnic and racial groups.

But comparing efficacy in those vaccines to the efficacy of Johnson & Johnson’s is challenging because of differences in the designs of the Phase 3 clinical tests — essentially the trials were testing for different outcomes. Pfizer’s and Moderna’s trials were testing for slightly different criteria, with Pfizer counting cases from seven days after receipt of the second dose of vaccine and Moderna waiting till day 14 to start counting cases. Both tested for any symptomatic Covid infection.

J&J, by contrast, sought to determine whether one dose of its vaccine protected against moderate to severe Covid illness — defined as a combination of a positive test and at least one symptom such as shortness of breath, beginning from 14 or 28 days after the single shot.

Experts say it does not really matter (and you likely won’t have a choice in most cases). Any vaccine you get should do a pretty great job at protecting you against severe illness, along with hospitalization and death.

From an individual standpoint, a slight dip in efficacy might not make a big difference, but from a population standpoint, it can translate to a lot more people who remain susceptible to getting sick and spreading it to others, Onyema Ogbuagu, MBBCh, is an infectious diseases specialist from Yale medical school said.

All of these vaccines working together will help us achieve herd immunity. We really need 65% to 85% of the population to have protection against the virus, Ogbuagu said. And that end goal becomes a lot more realistic when we’ve got a mix of highly efficacious vaccines.