Complete Vaccination Data: A Moving Target

The Coronavirus Resource Center (CRC) recently released a set of new visualizations to track COVID-19 vaccine administration across the United States. As shown for Maryland below, one of the new graphics highlights the proportion of people in the state who are “partially vaccinated” versus “fully vaccinated.” The CRC considers a person partially vaccinated if they have not completed the full dosing regimen for their vaccine type. This metric is critical to gauging an area’s level of vaccination since the number of doses administered does not directly correlate with the total number of people fully vaccinated because some vaccines require two doses. The partially vaccinated proportion also helps track if people are not completing the dosing regimen, which is becoming more common¹ and requires targeted outreach to solve.

The percentage of a population fully vaccinated continues to be key in assessing countries’ vaccination efforts. The world is not safe until everyone is vaccinated. The majority of global vaccination data acquired by the CRC have been sufficiently detailed to be useful so far. To appropriately classify the person as “partially vaccinated” or “fully vaccinated,” we need to know whether the person received a 1-dose or 2-dose vaccine and which dose they most recently received. However, the amount and types of meta-information required to categorize vaccination data points will change soon due to booster shots and mixed vaccine schedules.

Booster Shots

Booster shots are likely coming. The timeline is unclear, but manufacturers have begun announcing that additional doses could be needed.² Although the CDC and FDA say that it is not time for booster shots in the United States,³ Israel, which was a leader in the COVID-19 vaccination rollout,⁴ recently began administering booster shots to its immunocompromised sub-populations⁵ and those over the age of 60.⁶ As of July 22nd, detailed data on booster shots administered were not available on Israel’s COVID-19 dashboard. With the addition of booster doses, vaccination data reporting will need to expand to identify fully vaccinated populations. The dose number alone will not be sufficient to categorize people as fully vaccinated and the complications of additional shots necessitate vaccination metadata becoming more detailed. We can only properly track a country’s vaccinated population if information on all doses ever received is available.

Mixed Vaccine Schedules

Some countries are also considering administering different vaccines at subsequent vaccinations. Thailand has given AstraZeneca vaccines to those who already received the Sinovac vaccine⁷. The data on those individuals has not been published on Thailand’s COVID-19 dashboard as of July 22nd. Even if uncommon, mixed vaccine schedules add a new requisite to vaccine metadata – manufacturer types for each vaccine dose.

Mixing vaccine types was not formally evaluated in phase 3 clinical trials but may be sound scientifically⁸, and merits further study and continued observation. The timeline for additional doses may also be different between manufacturer types, so the transition of a group from “fully vaccinated” back to “partially vaccinated” when booster shots are recommended will be impossible to determine if countries do not report both the manufacturer of individuals’ first doses and the manufacturers of individuals’ subsequent doses.

Thought Experiment

To highlight the importance of detailed metadata, let’s say a country reports that a dose of the Pfizer vaccine (a 2-dose vaccine) was administered as a second dose to someone recorded as having received the first Pfizer dose weeks earlier (situation A above). That data point contains sufficient metainformation to classify the person as “fully vaccinated.” However, a different country simply reports that they administered a single dose of the Pfizer vaccine (situation B above) without documenting whether the person had previously received another dose. We cannot identify if that data point constitutes a “partially vaccinated” or “fully vaccinated” person, making the reported data difficult to interpret.

With the addition of mixed vaccines schedules and booster shots, we will need more information in each vaccination data point to appropriately categorize vaccination status. Knowing that the requirements to be fully vaccinated will be more complicated, one country (situation A above) reports that it administered one dose of the Pfizer vaccine to someone who already received one Pfizer dose. This information is sufficient to classify the person as “fully vaccinated” with the caveat that one day they may need a booster shot. No additional information is needed for classification. However, a second country, with lackluster data standards, simply reports someone came to a clinic for their second dose (situation B above). Without knowing the vaccine manufacturer, we don’t know if this person mixed vaccine types or will need a booster. The level of detail in the data as currently reported is insufficient.

Given these considerations, we have a critical opportunity to prepare for changes in the data reporting needs before they occur. With global economies, international travel, and the general welfare of humanity hinging on vaccination rates in every country, we need to establish rigorous vaccination data reporting policies if we want to cross borders once again.

As we enter this next phase of pandemic response, vaccination data needs to include information on vaccine type, manufacturer, and dose number. We have the roadmap to high-quality vaccination data – let’s follow it together.

References

1. C. Anders, 15 million people in the U.S. have missed their second dose of the coronavirus vaccine, CDC says, 02 July 2021. https://www.washingtonpost.com/health/2021/07/02/missed-second-dose-covid19-vaccine/. (22 July 2021).
2. M. Erman, J. Steenhuysen, Pfizer, BioNTech to seek authorization for COVID booster shot as Delta variant spreads, 09 July 2021. https://www.reuters.com/business/healthcare-pharmaceuticals/pfizer-ask-fda-authorize-booster-dose-covid-vaccine-delta-variant-spreads-2021-07-08/. (22 July 2021).
3. Joint CDC and FDA Statement on Vaccine Boosters, U.S. Department of Health & Human Services, hhs.gov, 08 July 2021.
4. B. Rosen, S. Dine, N. Davidovitch, Lessons In COVID-19 Vaccination From Israel, 18 March 2021. https://www.healthaffairs.org/do/10.1377/hblog20210315.476220/full/. (22 July 2021).
5. I. Kershner, Israel allows those with weakened immune systems to get a third Pfizer-BioNTech shot., 12 July 2021. https://www.nytimes.com/2021/07/12/world/middleeast/israel-third-covid-vaccine.html. (21 July 2021).
6. P. Kingsley, Israel will give third Covid vaccine shots to those over 60, 29 July 2021. https://www.nytimes.com/2021/07/29/world/middleeast/israel-third-shot-covid-vaccine.html. (29 July 2021).
7. P. Thepgumpanat, P. Wongcha-um, In first, Thailand to mix Sinovac, AstraZeneca vaccine doses, 12 July 2021. https://www.reuters.com/world/asia-pacific/thailand-starts-tighter-coronavirus-lockdown-around-capital-2021-07-12/. (22 July 2021).
8. D. Lewis, Mix-and-match COVID vaccines: the case is growing, but questions remain, 01 July 2021. https://www.nature.com/articles/d41586-021-01805-2. (22 July 2021).