Biden had received a second booster. Here’s why it wasn’t enough to prevent infection.

President Biden’s coronavirus infection clearly shows that the Covid vaccine is powerful, but far from the bulletproof shield scientists once wanted.

Biden has been vaccinated multiple times with the Pfizer-BioNTech vaccine. According to the White House, his latest shot, the second booster, was March 30th. Studies show that these doses provide a strong breakwater against severe illness. In fact, the president’s symptoms are mild so far.

However, even booster doses, especially with the latest versions of the virus, provide little protection against infection. The slight protection they provide declines rapidly and quickly. the study is showing. For the president, booster shots taken nearly four months ago may have lost most of his ability to prevent infection.

In the early days of the pandemic, experts believed that vaccines were sufficient to prevent not only serious illnesses, but most of the infections. And that was true when earlier versions of the virus, including the Delta variant, swept the globe.

However, Omicron variants have overturned those hopes. As more populations, whether by infection or vaccine, gained some immunity, the virus evolved to evade their defenses. BA.1, a subvariant of Omicron that circulated in winter, was good at causing infections even in people who received a boost just a few weeks ago.

Each subsequent viral avatar is even better at evading immunity. Currently, BA.5, which accounts for nearly 80% of US cases, is the wisest to date.Detailed data collected in Qatar show immunity from previous infections and vaccines Weakest against BA.5 Compared to its predecessor.

BA.5 is also highly contagious. The country records about 130,000 cases per day on average. Most people test at home or not at all, so that number can be very underestimated.

BA.5 does not appear to cause more serious illness than other forms of Omicron, but hospitalizations have skyrocketed in the last few weeks.

Given how much the virus has changed, the government is discussing the value of allowing additional injections of the original vaccine in the fall and providing a second boost to adults under the age of 50. Last month, the Food and Drug Administration’s advisory board required vaccine makers to create shots for the latest variants.

However, it’s unclear if these shots will be in time to prevent the fall surge, and if the virus has once again evolved out of their reach.