Booster vaccines are likely arriving but exactly who needs them and when is being debated. Pending FDA approval, booster shots for those who received either of the mRNA vaccines (Pfizer or Moderna in the U.S.) were initially expected to be available beginning Sept. 20, according to President Biden and Dr. Anthony Fauci.
A later statement by Fauci advised that since Pfizer filed its request first, the Moderna booster could be available a few weeks later than that. Moderna then announced its booster shots will be half the strength of the original shots, adding some complexity to the FDA’s consideration.
Data suggest that while the ability of the vaccines to prevent severe disease or death remains strong, the ability of milder infections to “breakthrough” and infect others seems to be increasing. It’s not yet clear how much of that is due to waning protection of the shots or an increase in the Delta variant’s ability to spread, and there are justifications for and against boosters.
The CDC recently authorized (under an EUA) a third dose for severely immunocompromised individuals four weeks after their second dose of an mRNA vaccine. That’s because these individuals, people undergoing chemotherapy or who have HIV, don’t produce enough immune response to the first two doses. These are not booster shots, but an attempt to give these folks the same protection against the virus as others. The booster shot is designed to stop the immunity achieved from the first two doses from diminishing.
Argument for the booster
Israeli data reported in August showed that rates of infection are increasing for those over 65 who were first vaccinated in January or February. Further analysis shows that the number of antibodies is decreasing several months after vaccination and that the vaccine may now be less effective in preventing infection from the virus. Some breakthrough cases are symptomatic and there is a trend beginning to show, in several countries, of breakthrough cases requiring hospitalization. Most of the breakthrough cases are from the more infectious Delta variant.
Since there is evidence that people with Delta-caused breakthrough cases can transmit the virus, the waning levels of antibodies is troubling. Booster shots are nothing new; in the U.S. there are boosters at various ages and time intervals for flu, TDaP, varicella and others depending on a person’s age and profession.
“The science is the boosters work, and they will definitely help,” Shane Crotty, a virologist and professor at the La Jolla Institute for Immunology’s Center for Infectious Disease and Vaccine Research in California, said. “It’s a race between the virus and your immune system.” The faster the virus replicates, the less time antibodies will have to block the virus. The more the virus replicates, the greater the chance of more and possibly more dangerous mutations.
Argument against boosters
The World Health Organization has come down hard against plans to initiate booster shots when many countries are still without ability to afford a vaccine or manufacture their own. Fauci has said that the U.S. can do both, sending doses to developing countries while providing boosters as well.
WHO refutes this, saying that poor countries shouldn’t have to be satisfied with “leftovers” from wealthy countries. Furthermore, the virus is a worldwide danger, and the more people who become infected, the more potential for new mutations, possibly some that could defeat current vaccines.
There is also contention over whether there is any need for a booster in the first place. Some in the health care business note that the primary purpose of vaccines is to prevent severe illness and deaths, and that the vaccines are doing that quite well. They argue that the most useful expenditure of money and effort right now would be to get more people vaccinated, and not to administer extra doses to prevent what is usually only a mild annoyance (the typical breakthrough case.) This argument ignores breakthrough infections increasing the spread of the virus and the danger of possible new mutations.
Another area of disagreement is the efficacy of the booster in real life. Although data exist that show boosters ramp up antibodies, there is no evidence yet that this translates to better ability to stave off an infection or lessen hospitalizations or deaths.
Future of boosters?
They’re probably coming soon. Walmart stands ready to deliver millions of shots. Moderna has announced that it’s manufacturing a combination Covid-19/influenza booster, both mRNA-based. The FDA has not yet approved the boosters, but it’s widely expected that an Emergency Use Authorization will be issued at least for those who are elderly or otherwise at higher risk of breakthrough infection and serious issues if infected.
Both Pfizer and Moderna are gearing up to make and deliver booster shots, and Johnson & Johnson is now saying that an additional shot produces a more robust antibody response than those who received just the one dose of its vaccine.
Fauci said that while there may not be an annual need for a booster, the vaccines may simply need to be delivered in three doses for optimal results, as are some other vaccines.
There is also the possibility that emerging variants will require variant-specific boosters. Whether that would be a one-time event or recurring booster like the annual flu shot is unknown.