Despite this, doctors are still urging everyone who is able, to get vaccinated against the virus.
As of Sunday morning, more than 225 million Americans have gotten at least one dose and about a quarter of the population is fully vaccinated.
However, a trend some health experts are starting to see is people skipping their second dose of vaccine.
Top health officials said the increase in missed second coronavirus vaccine doses was anticipated with the increase in eligibility, but they are now also focusing on figuring out why this may be the case.
Doctors and experts concerned about what this could mean in the long run are worried that the millions missing this second shot could impact herd immunity in the battle against COVID-19.
New data from the Center for Disease Control reported that only 92% of people are completing the two-dose series of Pfizer and Moderna vaccinations. That means about 8% of those eligible may have missed their second dose.
That 8% translates to about 5 million Americans.
"That means that we're not going to be able to reach herd immunity as quickly as we would like," said Dr. Zachary Rubin, a clinical immunologist.
Health officials are now reminding those that have missed their second dose that it is necessary in order to provide full immunity and to be considered fully vaccinated.
Why is this happening?
Authorities are still working to figure that out to see if missed doses or delays are due to access, meaning supply or vaccine availability, or even vaccine hesitancy.
"With one dose of the mRNA vaccine, we don't have enough studies to see how much effect that has long term. We know that it does confer some effectiveness, but it's definitely far less than getting a two-dose series," Dr. Rubin said.
Dr. Rubin added that while some said they feared the side effects, many others recently reported their second dose appointments were canceled by large pharmacies like Walgreens
Walgreens issued a statement to ABC7 that read:
We're pleased to share that our second dose completion rate is nearly 95 percent (note: this is for those who received dose #2 by 4/18).
We had an earlier scheduling glitch for people looking to get their second dose at a different store from where they got the first dose. This impacted a small percentage of those who had scheduled their appointments online. We resolved this back in March, and at that time we reached out to those who were impacted to assist with rescheduling their appointments in alignment with our vaccine availability. For the majority of these patients who we helped navigate the glitch, it was not about a lack of availability of the right brand for second shots. This was confined to our scheduler and was addressed and corrected last month.
Since the onset of administering vaccinations, we are committed to honoring all appointments and ensuring patients receive their second dose. In fact, our second dose completion rate is nearly 95 percent (as of 4/18/21).
The pharmacy said it reached out to those impacted and the glitch was resolved in March.
This comes as local health departments are expanding vaccine access by offering walk-in appointments and bringing back the one-dose Johnson and Johnson vaccine.
"We need to try to get those second doses into people's arms as quickly as possible," Dr. Rubin said.
For those who have missed their second dose recently, the CDC said it's not too late. You can still get your second dose if it's six weeks after the first dose.