CDC’s Booster Plan May Not Provide Optimal Protection

TLast week, the FDA and CDC approved updated bivalent COVID-19 vaccis. The promise made by the mRNA vaccination technology platform was that they could be updated quickly. The updated vaccine recipe is compatible with the current dominant BA.5 strain and slow-growing BA.4.6 strain, so we may have finally achieved an edge over SARS.COV-2.

We are worried that the CDC could be again ignoring the timing recommendations for Americans to receive the booster. Following its Advisory Committee on Immunization Practices (ACIP) meeting on September 1, the CDC stated that adults who completed their primary vaccine series are eligible for the updated booster if it’s been at least two months since their previous vaccine. The CDC advised people who have recently been infected to wait three months before they get boosted.

But, this short time interval could be detrimental if we want strong protection against re-infection. Two reasons why the CDC suggests a 6-month period between a prior booster or infected vaccine and the current updated vaccine should be considered: 1) updated immunologic research and 2) recognition that millions had Omicron variants post-vaccination. In this way, there is strong protection against re-infection.

Studies in immunology

The CDC was previously asked to increase the interval between the primary doses for both mRNA vaccinations to 8 weeks based on immunologic studies that showed a greater antibody response and amplified T cell responses, as well as enriched memory cells which have a shorter time between doses.

Studies from Omicron variation era have shown that a prolonged interval between doses is beneficial in increasing memory B cells as well as neutralizing antibodies. Recent research has shown that boosters provide antibody protection for at most 6 months. A second study showed that both those with previous infections and those who had received vaccines for the first time experienced stable antibody levels 6-9 months after vaccination.

Memory B cells were even more robust after vaccination–demonstrating maintained reactivity against all variants including Omicron for at least 9-10 months after the primary 2-dose series; with an additional positive response to a 3rd dose booster. Another study found that memory cells matured for 6 months after infection or vaccination. B cell immunity—as well as T cell immunity to COVID vaccines–provided protection against severe illness and did not lead to high levels of hospitalization as BA.5 became dominant this summer.

Read More: Why You’ll Need to Get COVID-19 Boosters Again and Again

Omicron-specific vaccines have the goal of increasing antibodies to prevent mild infections. A 6 month antibody plateau would signal that it is time to start a BA.4/5-focused vaccination. This is because a lower pre-boost antibody levels correlate with an increase in the number of folds after boosting. To put it another way—high levels of circulating antibodies from short interval boosting may limit the added protection of another booster. Another study from the NIH found that effective B cells responses are affected by boosters given 2 months after a recent infected.

Omicron has infected millions

JAMA published a study that found 56% of Omicron-infected people were unaware they had the disease. The actual daily infection rate for this year’s Omicron variant was far greater than that reported by the government, due to the large scale of non-reported rapid antigen test results at home. Millions of Americans also received their fourth and third vaccine doses within the past few months.

This level of population immunity is evident in a new study from Portugal that shows, contrary previously held concerns about BA.5 reinfection, that previous BA.1/2 infections provide up to 75.3% protection against the possibility of re-infection by BA.5. A Qatar study found 79.7% protection against reinfection.

These data indicate that COVID-19 is highly protected against severe diseases in America. This immunity should be recognized and augmented in order to prolong the shot’s protection throughout winter. A short-term repeat boost or too early a booster after a post-vaccination illness will decrease the antibody response. This can cause memory B cell expansion to be slowed.

The CDC revised its guidelines after receiving extensive expert input. In February 2022, it recommended an extended interval of dosing for the primary series vaccine. This was significantly less than the recommendation by their counterparts in Canada. Europe and India also adopted this interval. The extension of the vaccination interval wasn’t widely advertised. Now, the CDC has an opportunity for improved performance of these immunologic principles to update Omicron booster.

Canadian National Advisory Committee on Immunization has already recommended, in writing, that the new bivalent vaccine should be available at a time of six months from the date of previous vaccinations or infections.

In a recent survey by the CDC, 72% of those polled will “definitely” or “probably” get an updated booster. This is significant as only 50% of Americans were able to receive the recommended booster dose, and 34% only of those aged 50 and over received a second booster. This is why we need to get timing guidelines right for Omicron booster update, the first update of the mRNA vaccines.

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