The Covid-19 vaccines have been available in the U.S. for around 9 months, and researchers are continuing to study their effectiveness, specifically questioning how long the protection they offer will actually last. And now, a recent analysis conducted by Moderna, who makes one of the two mRNA Covid-19 vaccines, has shown that the effectiveness of the vaccine decreases as time goes by. In fact, according to the study, people who got the shot last year are twice as likely to contract the virus as people who recently got the shot. Moderna is hoping that this new data will lead to approval of a third-dose booster shot for those who received the original two-shot dose.
The Study
The trial conducted over the summer by Moderna, labeled the 3 COVE Study, compared participants who received the vaccine between July 1, 2021 and August 27, 2021 to participants who got it between July 2020 and October 2020. Analysis of the data revealed that people who had recently received the vaccine had a lower risk of breakthrough infection than people who had been vaccinated last year. Specifically, “88 breakthrough cases of COVID-19 out of 11,431 people vaccinated occurred in the more recently vaccinated group (49.0 cases per 1000 person-years) compared to 162 cases out of 14,746 participants in the group vaccinated last year (77.1 cases per 1000 person-years).”
The study found that people who were vaccinated last year had a 50% higher rate of symptomatic breakthrough cases during the months of July and August compared to those who had received the vaccination later. And of those who received the vaccine more recently, there were no hospitalizations or deaths, compared to the 3 Covid-19 related hospitalizations of the earlier group, which resulted in 2 deaths.
“There’s a large debate, we all know, about whether or not vaccine boosters are going to be necessary in the fall,” Moderna President Stephen Hoge said. “That debate, what makes it really hard is it’s not really about whether the vaccine worked last month. It’s really about whether it’s going to work this winter.”
Is There a Need For A Booster Shot?
When the study and its data was presented, Moderna CEO Staphane Bancel stated that it proves the need for a booster shot. 
“It is promising to see clinical and real-world evidence adding to the growing body of data on the effectiveness of the Moderna COVID-19 vaccine,” Bancel said. “The increased risk of breakthrough infections in COVE study participants who were vaccinated last year compared to more recently illustrates the impact of waning immunity and supports the need for a booster to maintain high levels of protection.”
Currently, the White House’s plan is for people to get a third dose 8 months after their second shot of either the Pfizer or Moderna vaccine. However, multiple scientists from the World Health Organization and 2 FDA officials claim it is “not appropriate” to widely distribute booster shots to the general public just yet.